Finally got around to looking at this. My 2910 wouldn't raise the 3 point until the control hit between 3 and 4 and would keep raising it beyond 8. There is a threaded rod with lock nuts on either side of a connecting lever (follow the 3 point lever down to the HST case adjacent to the rear wheel). If you adjust the locknuts down towards the end of the threaded rod it will begin lifting your 3 point sooner. I moved mine as far towards the end of the rod as I thought prudent (left two threads protruding) and my 3 point now begins to lift around 1 1/2 and stops lifting at around 8.
Doesn't seem right, I think that lifting operation should occur with the locknuts set on the middle of the rod.
Dave