The PVC glues inside the scupper flange, and the scupper flange glues into the hull for the Xmetal scupper. I've never seen a 24/7 scupper in person, if i remember correctly the pvc glues into the hull and the scupper flange screws to the hull? (its only purpose is to support the flap?).
If thats the case you could use an Xmetal scupper I believe, but youd have to redrill the hole a bit larger for the xmetal flange to fit.
I dont have the measurements on me though.... so I could be wrong.
LBE: The flap on the xmetal scuppers is held on by 2 screws, its easily replaced. As for the flange itself, I dont think there will be any problems with it coming lose or breaking or tearing... The first xmetal scupper I put in shifted slightly overnight while the the epoxy was curing... Id rather defoam a ski 3 times than try to remove that scupper again. I had to cut the pvc off through the scupper hole, and hammer the tube out with a baseball bat and 10lb hammer. If I had my holds in it would have been impossible to remove....