Anyways, I already reread and realised I did miss something. Zerotacg is saying that the max XP is reached for a 50 lvl difference between Q1 and L whereas Berrule said in the original post it is reached for a 50 lvl difference between Q2 and L. From my experience I would say Zerotacg is right; the experience is capped before the degrade multiplier is applied, and not after.
This is the same with foraging experience where the multiplier from explosions or source death is applied after the cap, but unlike hunting experience where the cap isn't applied until after all multipiers have been.