I had zero issues with the Serpa not fitting my Hicapa slide...and it wasn't tight at all (I have it set at it's most open setting).
I'm not sure if it's a more recent Serpa mold or not...but after taking a close look at the trigger guard area of the Serpa...I opted for reprofiling the trigger guard of the pistol vs. hogging out the holster. I just wasn't sure that there'd be enough material left in that area of the holster.
The Serpa material seems really thick (at least on the one I have)...not the typical kydex sheet sort of thing...it'd take a lot of controlled heat to nicely stretch it. With my luck I'd end up with a pile of goo.