Hi Jim,
Thank you for your comments, suggestions and questions.
Acratech makes high quality gear and they have some unique designs that seem to be especially suited to photographers who hike. Keep in mind that when you set aside advertising hype, every solution is a compromise and it is up to you to decide what compromises you are willing to accept. I see three problems with the Acratech panorama head you reference.
1) The rotation mechanism is beneath the single tilt mechanism. If you are going with a panoramic head with a single panning mechanism, for my money it is better to locate it above the tilt mechanism (see Arca-Swiss p0 and P1)
2) It only incorporates a single tilt mechanism* which is oriented along the pitch (fore/aft) axis (assuming you are using a rail to put the entrance pupil or virtual entrance pupil over the yaw (horizontal rotation) axis. To level the roll ( side to side tilt) motion requires either a leveling base underneath that Acratech head (which Acratech notes or leveling the base of the head by adjusting individual leg lengths.
While you could mount it on top of a heavy duty head like your Really Right Stuff BH-55, an Arca-Swiss Z1, or similar ballheads or a heavy duty "rational" ( double tilt + panning base) tripod heads, and use that larger heavy duty head as a leveling base that just makes things much more mechanically complex, bulky and heavy. Andthe panning mechanism will still not be at the camera platform level. Any tripod head, ball or rational design, that has hat is below the panning joint is essentially
3) The ultimate solution is to have two panning joints: one at the base and one at the top of the head - the way Arca-Swiss designed the C1 "Cube" , D4, and D4M and Induro builds the PHQ-3.
If you are strictly a landscape photographer where all of the subject matter is at infinity for the lens you are using to shoot stitched panoramas it may make little to no difference whether you have the panning mechanism above or below the tilt mechanism(s). However most of the panoramic work I do is very high resolution architectural and industrial work where I have a lot of intricate foreground/background relationships and from experience what I have found outthe hard way is that I do indeed need a panning movement above the tilt mechanisms. I also prefer to do panoramic work with a rational head rather than a ball head for the simple reason that the pitch and roll controls are separate. Separate leveling controls are easier to work once a camera or a large panoramic rig is mounted on the head.
At this point I don't need another limited function head like the Acratech head. A couple of years ago I lucked into an eBay auction and was able to purchase the very heavy duty (and heavy) Foba ASMIA head (
http://tinyurl.com/Foba-ASMIA) for an outstanding low price, and I also use Arca-Swiss D4M (
http://tinyurl.com/ArcaSwiss-D4) , p0 and B1 heads. To the ASMIA and B1 I've added Really Right Stuff PCL-1 panning clamps. With the PCL-1 topped ASMIA, I have a range of motion that meets or exceeds that of any ballhead.
My quest is to replace the PCL-1 on the ASMIA with a heavier duty version of the PCL-1.
* There is nothing wrong with single directional tilt heads for other uses like using with a monopod. Sinar also makes or made a really heavy duty single tilt head that works great for their large format monorail cameras where you can adjust the roll angle by rotating the monorail in it's tripod mount.
Post script: As a result of this post both Mr. Johnson and an engineer at Really Right Stuff got in contact with me updating me on the progress of what I am calling the "PCL-2". I appreciate their forthrightness. 
