There are "Shark Bite" fittings for COPPER tubing, and similar ones for the "PEX" tubing used in RV water systems. Just cut the tubing clean and square, push into the fitting, it's done.
I raised our toilet (Thetford AquaMagic IV) using a Pedestal. I found that a PEX shutoff valve (Shark Bite design) added about the height of the pedestal to the length of the supply line. Cut the line and installed the shutoff valve I wanted anyway. Came out just right.
EDIT: Oh, RV toilets use a Foam Ring instead of the Wax Ring we use at home. Much less messy.
