I'm certainly not an expert on full hydro steering, however in talking to my brother who is currently designing his new rig (front and rear steer Axletech 4000's on 54" ag tires), pump flow seems to be a major concern. Depending on the ram size and stroke, system speed will be determined by flow, so if you're marginal in any way, I imagine that will mess with the hydroboost. The orbital valve displacement combined with the hydraulic cylinder volume will determine the lock to lock.
There are hydraulic prioritization valves, but which do you prioritize...brakes or steering? They're both pretty important.
FWIW, KOH rigs like Hell's Bells (666) running front and rear steer run Howe Performance trophy truck pumps with something like 11GPM flow rates, but that's a $1300 pump IIRC. Other guys with the big Havoc type buggy/truggy applications run more conventional Saginaw type pumps (one or two), and then a separate electric over hydraulic pump for the rear steer, since it only sees intermittent use, but none of the ones I saw up at Mountain Havoc this year were running hydroboost that I could see anyway. Most were manual brakes, and an couple were vacuum assist.