I think I know the answer to this but wanted to see if anyone knew for sure. Will a holster for a 225-a1 fit a non rail 229? I think it will.

It might, depending on the cut. FWIW, though, SIG's website lists the barrel length for at 3.6" for the (current?) 225A1s and at 3.9" for the 229.

Fit and fit correctly are two different things. Holsters aren't socks. I've tried to fit pistols into holsters that were not intended for the pistol. It "fit" ok but didn't retain well at all. The poor fit might also cause finish wear.

Leather is more forgiving that Kydex but "fit correctly" still applies.

This one does. Not all will. I imagine over time switching between the two it will no longer fit well for the 225A-1. Currently my M11-A1 is super tight (almost too much), the 225A-1 is a much easier draw. Best thing to do is see if both are listed on manufactures website or call them.

They will not fit correctly 80% of the time. I do have one Bianchi holster that fits all of my Sigs. I believe it is a black widow model, with a thumb strap. My p226 is tight, while the p225a1 is not perfect, but safe for carry.