I mounted my Altrider rack in the low position the first time. Then I needed the passenger seat and grab rails so I put it up. Either way the case is still too far back. But if it were moved permanently forward and low, then the grab rails and passenger seat have to come off and stay off. I'm still trying to decide what I want to do about this - I rarely carry a passenger, but never say never.
Right now, even with a passenger and the rack in the high position, the case is still too far back. I don't carry a passenger often enough that I would put a backrest on the case - those Givi backrests are too high for proper support, less comfy than just leaning on a plain Givi E45, especially when the passenger is wearing a jacket with a back protector. So at the very least, that case could come forward maybe 1.5" to 2". It would foul the grab rails, in the low position, but the high position would allow the case to come forward.
I could put it in the high position and make a sliding mechanism of some sort, and cantilever my top case forward over the passenger seat when I'm not carrying a passenger. The case would have to go up a hair higher, though. Is it better to go higher and farther forward, or leave it back and down, or give up the grab rails and/or passenger seat?
What will make me happiest? I haven't decided. So for now, I'm running it as is, in the high position. Pity the grab rails are the way they are!