I also took up Hand paddling, and gained a whole class for it.  I keep hearing that there's an upper limit that is lower for HP's than for stick paddling.  However, everyone has a different figure for that.  For now my arbitrary limit is no HP's for me on any river that is fast with must make moves with limited space.  This still enables me to run stuff like Upper/Lower Gauley, Cheoah, and probably the Tallulah which is on my list of rivers to do soon.  However, I am not sure if I should HP or stick paddle the Upper Yough which is next on my list.  I will probably stick paddle it first, and bring my HP's in case I decide that will work better when I am in the thick of it.

Now I'm not a horrible stick paddler, and I've gotten out on the lake a few times to bone up on different rolls with a paddle, I am still way better as a HP'er.  And much more comfy too.

My suggestion for anyone who is still trying to do both styles of paddling, and this is what I did, is to get a Lendal 4 way breakdown with the adjustable range 0-90 offset.  They also offer an adjustable lenth size adjusting model too.  This way you can tune the paddle to yourself better.  That way I HP all the stuff I want to HP, but have the stick for those features I want to attain (Such as surf waves) but need more driving power to get to, and those rivers or sections/rapids where a stick makes more sense (Such as must make power moves in fast current).  This way you can carry both and not be limited.  It also insures for safetys sake that you have some sort of backup paddle.