On one of my RIAs, a compact, the receiver is actually pretty good but the slide is awful in just about every way imaginable. I put a Kimber compact 22 slide on the receiver and that combination is very close in size and weight to my Sig Ultra Compact 45 carry gun. (RIA w/22 slide has aluminum slide and steel frame, and Sig has steel slide and aluminum frame). I then completed the build with an extended magwell and G10 grips similar to the ones on the Sig. So I can take the RIA/Kimber (RImber?) to the range and shoot a bunch of 22 ammo through it, then seamlessly switch over to the SIG which feels exactly the same.
Every once in a while I kind of forget why the RIA slide is awful and put it back on and take it to the range and immediately remember why I don't shoot it. Maybe I should get a Caspian slide for it.