Yeah, my version of quickload didn't have it either, even though it had been out awhile when I got my update.
I've used PP300MP in the 350L and 357 Max, but not with the bullets you're using. According to my loads, going with H110 starting data should be a safe bet. My loads with MP topped out about 1 grain higher than my 296 loads with the same bullet.
FWIW, Quickload doesn't seem to be terribly accurate with these cartridges anyway.
