If you can use a screwdriver and a lens wrench / lens key then you could mount your own lenses. There's no helical on the Arca mount, so as long as it's machined correctly my cat could do it. He could mount it for an Alpa or a Cambo as well come to that, even the T/S Cambo mount (and he's a real dummy, spends most of his time chasing his tail and getting his belly rubbed).
Of course, the problem is you can't actually buy the mounts - and no enterprising far-eastern engineering student on eBay has yet figured out that this is a potentially lucrative business opportunity staring them in the face.
I'm sorry, but the attitude that 'it has to be done at the factory' is the photographic equivalent of 'rust-proofing' in 'The Dealership' epsiode of Seinfeld*. I've mounted/unmounted any number of lenses in a variety of helicals/mounts/lensboards over the years without a hitch; I just remounted a 47mm digitar onto a Fotoman helical and mount for a friend, adjusted the lens for infinity focus and bingo, she creates tack sharp images as every bit as wonderful as those I've seen produced by the same lens in Alpa and Cambo mounts - and for a whole lot less than what the 'big three' charge.
Since Henry Fox Talbot fell head first out of a tree we've been tweaking helicals and taking lenses apart, cleaning the shutters, screwing them back together, carting them around in cases on planes, trains and automobiles, knocking and bumping them, getting them baking hot and freezing cold, soaking wet etc. - but now in the digital age they have all suddenly become so fragile and delicate that attaching them to a dumb old helical and then to a piece of machined metal (and perhaps installing an angled sync and cable release socket) is, apparently, beyond us. This can now only be done in hermetically sealed rooms by folks in white coats with PhDs and exotic accents (at least, that's the scenario I imagine). This is utter madness.
Whilst I understand that this is a lucrative part of the business model of these companies … at the end of the day, from the perspective of the end-user, this is all about choice (or, more correctly, the lack of it). If you want to send your lens away to be mounted then great, go for it - but if not, wouldn't it be nice to have the choice to do this yourself?
Thinking about it, I would even pay 75% of what they are asking to do the work themselves if they would just send the hardware straight to me. That's right, I'd pay them to do nothing other than ship the parts. It'd be worth it for all the stress and hassle it would save of 'temporarily exporting' expensive lenses and the 'temporary importation' of them on the other end. I once sent some lenses to be retrofitted to one of the 'big three' and the 'advice' I got was to mark the shipment as 'lenses for repair' and value it for under $100 - so they didn't have to pay any import taxes, as they had no facility to 'temporarily import'. Er, ok, but you know what, you can't insure a shipment for less than it's declared value, so if it goes missing, who's going to pay? I would have got $100 for $4k worth of lenses - or maybe they, or the overseas dealer that was handling the money side of things, would have reimbursed me (er, right). Looking back, I realize that I was effectively railroaded into breaking the law by giving the false valuation and misleading description (a combination of naivety and necessity got the better of me that time, but I wouldn't do it again). And I paid over $3k for the pleasure, sheesh. I wonder if this is the deal with the other two of the 'big three' - do they have the facility to 'temporarily import' items (which is a fairly involved procedure, usually requiring the posting of a bond of some description to make sure the goods are exported again), or is everything shipped to them with 'a nod and a wink', trusting FedEx or UPS to deliver everything in good shape … interesting, because (as mentioned above) deliberate under-valuation or falsification of the customs declaration (e.g. stating 'for repair' - thus implying little or no value in the present condition) is illegal from here to Timbuktu. Any A/S, Alpa or Cambo dealer like to comment on how you handle this when you send lenses to be retrofitted? I guess if a company has no 'temporary importation' facility for me, they don't for you either? So, what do you do? Maybe you dodge the bullet and get your customer to ship their lenses direct (as in my case) and let them sweat it? If so, what do you advise them to do about insurance and custom's declarations?
*For no one familiar with the episode of Seinfeld I refer to, Jerry goes to buy a new car and is almost forced into buying the expensive rust-proofing, which is both pointless and expensive … but the dealership insists is absolutely necessary. Eventually Puddy (the salesman) acknowledges that, 'Oh, we don’t even know what it is'.
** Quick thoughts on the Fotoman dmini, since no one ever mentions Fotoman cameras. From my brief time with it - Positives: Nicely machined, helical is good, feels solid, decently finished, great value for money (the body, grip and viewfinder cost less than Alpa's viewfinder alone), and they've since released an adapter plate that is adjustable to +/- 0.3mm. The helicals are particularly nice because they're 9cm in diameter, so the distances aren't as crowded as on the smaller Schneider ones - would work nicely with precision focussing rings (if Fotoman made them). The viewfinder is better than Cambo's (which, for the money, is abysmal), not as good as Alpa's or Arca's (Arca's is the best I've seen, but personally I find them all horrible to work with). I prefer the way the masks fit on the Fotoman to those of either Alpa or Cambo. The helicals also offer 1.5mm more travel than the Schneider's, so you can focus closer. Negatives: Don't like the way the lens attaches (four thumb screws - just like Horseman - too fiddly), the distance markings on the helical need checking, and the adapter plate is screwed on (you can change it, but need a screwdriver). All in all, if you want a really compact tech camera for under $1500 all-in (body + grip + viewfinder + mount + helical) then the dmini is one - perhaps the only - option ... and Fotoman will happily sell you the helicals and mounts as well for future lens purchases. I believe they will also custom make mounts for the same cost as the standard ones they sell (do ya hear me Arca, Alpa and Cambo? Custom mounts for the same cost - now that's customer service).