you can't really tune a Q-logic any lower unless you cut the back off or the side and extend the vent length, but isn't a Q logic a port tube and not a vent. I hate those. You'll be missing alot from the RL-p and probably won't like it with that box. I'd get a sealed one or a custom made vented box, and yes it'll do fine in a 1.75cu ft box.
if your gonna spend 270 bucks on a nice pice of equipment like the rl-p. i would recommend on a. building your own enclosure or b. find someone to build you one. cus your not gonna get the full potential of that sub outa that box