Here's what I could find, X means I didn't find any upper size limit. That doesn't mean there isn't one.
IS = X
DT = X
123 = X
SV = X
SS = 25MB
BS = 25MB
FT = 20MB
StockXpert = 16MB
I ran into a potential problem and the files when converted to JPG and saved at level 12 are about 13MB. There's hardly a difference at 80% or level 10, but I like to make them the best that they can be.
It's already reduced almost 20% and starting to lose some details. Next step and I'll be getting rejected for "jaggies". And I don't want to get rejected for file too large. I'm guessing I'm just under the Max. for StockXpert so that answers the question.