I've got the HiViz on my GP100, too, GOF.  With the 625 JM I'm going to try the SDM so I'll get a good idea of which I like best.  The GP100 does have interchangeable front sights and the 625 JM has even easier to interchange front sights.  The Ruger has a plunger in front to push in (requiring a tool) and with the JM you just push the sight back, with your fingers, past a retaining pin and rock it off.  My JM (from Buds guns) is a well made revolver.  The chamber throats are all right at .4525 and the forcing cone looks well machined.

I've got the fine emery cloth out and ready, but I just can't bring myself to start modifying my trigger.  I keep thinking that it didn't hurt my finger all that bad and maybe I should give it another match or two before I start removing metal.

Scott