The fu and the redfin will do fine together as long as the initial size differential in on the mark (we've had 1" specimens that would indeed become "fu food"). In fact, we have a juvie now and had to put a visual block between the little HOB fuge it's currently in and our juvie fuzzy lion setup as all the fuzzies want to do is eat it, and it drives them crazy that they can't get to it.
FWIW, the correct binomial for the redfin waspfish is Paracentropogon rubripinnis. Hypodytes is an older taxon that is no longer used. As for pygmy...all waspfish are small. I realize the latter is easier to spell, and possibly remember, which likely accounts for its continued usage.
Redfins are really great fish, and are fairly easy to sex, esp. as adults.