HK UMP 45 upgrade

Anyone have any ideas on mods for the UMP 45? I already have a alloy barrel.

I just bought one as well. Would be keen to hear suggestions.

I have just received my UMP 45 and put a longer alloy inner barrel, alloy outer barrel, alloy silencer ( for looks and to hide the inner barrel length ) and metal rails.

I have just ordered a metal gearbox, metal gears, shims, 1.3 spring, green rings, metal trigger, alloy plunger and head kit.

I really like the UMP 45, it feel solid, except the folding stock pin, it comes out a few mm after a bit of use.