At one of the GSSF matches right after the introduction of the gen 4's I recall the armorer saying that there was a difference in how the 4's are assembled. I think he was talking about the trigger mech housing and trigger spring orientation. What should I know about assembly or disassembly of a Gen 4? Are there any other differences? Besides the mainspring assembly/slide, magazine release and the difference in the grips, are there any other unique parts to the gen 4's?