Jason, the trim does depend both on the skill of the diver as well as the rebreather that is being used. When the counterlungs come over the shoulder the position of the diver in the water shouldn't matter much, at least that's my experience from diving the PRISM. Left to right does make a difference of course.
Things are different when you use a rebreather with rear mounted counterlung(s). They usually have a 'sweet spot' where the least hydrostatic difference between lungs and counterlung(s) offers the best work of breathing. If you look at different RB designs you'll see the CL are in different position. On the Dolphin and Azimuth high up towards your shoulder, on the MK series pretty much all across your back, on the Sport Kiss in the small of your back, on the RB80 all the way down by your butt. Each of them has a sweet spot, and on each of them it's gonna be a different one. Takes just few minutes of trying and you'll find it.
Another factor of course is trim balance, the Inspo for example has a weight pouch on top of the case, the PRISM one behind each counterlung (I use 5 lbs on each side), the MK has a trim weight bolted into the top of the case, the Azi has the huge ss handle on top. Bit harder on the Dolphin, no place provided as far as I recall. No issue with the Sport Kiss, the lungs are on the bottom where the valves are, as well as the normal weights. Kinda balanced itself pretty much.
I'm sure you've seen plenty of pics of RB80 divers in perfectly horizontal trim.
I dive the Sport Kiss fairly close to it. Having played with a MK16 in the pool I remember being able to get fairly close, but probably was another 10 degrees or so off horizontal for comfort. The Atlantis/Dolphin units I tried over the years where more in the neighborhood of what you mentioned, I would guess about 40 degrees. You dive where you breath the most comfortable.
Tried uploading pics, but that never seems to work here at Scubaboard.
If it's important PM me your e-mail adress and I can send them.
