Another factor is something that I understand is true about
NiMH cells in general (not just the low-self-discharge type):
charge acceptance is quite poor at low charge rates.

I've heard this as well. Specifically, at "low" charge rates (which which
would actually be on the "high" side for nicads), NiMH cells are less likely
to enter the negative delta-V region that indicates end of charge.

Having grown up with nicads, I'm reluctant to charge faster than 0.1C, but
it appears that 0.3C and even 0.5C is acceptable with good-quality NiMH
cells.