Yes, Gareth, that is what I dislike about the D1s. Actually, I don't think I have found any monolights that I really like, but I kind of think that is par for the course. If you want to save weight, and your back, you have to sacrifice in other areas.
I think I really need to get into high production shoots where I have like 3 assistance and a digital tech running around carrying everything. But, even so, I know that with the guys who do that work, that that only happens maybe a third of the time. The rest, they are working on small budgets with one, or two, assistants carrying half the stuff themselves.
Anyway, the Magnum reflector is pretty awesome. And if you have some money left over, I would highly recommend getting the Narrow Beam and the 10 degree grid spot, which fits both.
Both of those reflectors offer so many possibilities.
The great thing about the Magnum is the inside must have over a 1000 dimples, which keeps the shadow from breaking apart. In the kitchen image below, the light coming in from the left is from the Magnum, no gel (other than for color) was used.
Now the Narrow Beam has a polished interior, so the shadows start to break apart, but a 1/8 diffusion over the front (or under the grid) helps that. However, the Narrow Beam produces an extremely bright center with a dramatically less bright edge. This is great for me; I can aim the center of the beam to project the furthest into the image and still have that area brighter then where the edge hits. In the restaurant image, the Narrow Beam is about 5 feet outside the window on the right and is what is producing the light raking across the bar and making the light & shadows on the left.