Thanks Jon, I'll have to take a look (I haven't yet) - it really hasen't bothered me, I just chalked it up to the limits of the power steering system, and to my habit of running the engine at lower RPMs unless I need the power. I really have no idea at what RPM the hydraulic pump tops out.
To expand, I get some really heavy buckets with the Rhino FEL, and have no lift problems, but I often drop the engine speed back pretty quckly afterwards. I've never really taken notice if this is when I see it, but I will try to pay attention next time.