The 'grip chop' is not officially endorsed, but if done correctly it is not necessarily frowned upon - at least on a Service 9mm. There are no moving parts in that area of the gun so just be really careful with cutting it to the correct length and contour. My understanding is that if it breaks due to something unrelated to said chop they will still honor the warranty, and I can't reveal my source on this. YMMV, especially with a .45...
I will say that if I get a Service 9 it will chopped right after function testing, and my XD(m) may get it too one day if they actually introduce a shorter-grip variant :twisted:
That said, there is certainly wrong with playing it safe!
*Personal note/opinion: I have no desire for an XD with a thumb safety even though it is well placed, and never use the ones on my Makarovs except to safely decock them after chambering a round from a mag. If my guns aren't holstered they are in a secure casing of some type. A rumor has it that the thumb safety on the .45 came about from SA trying to get some government contracts but I do not know if that's true.*