[Snipezilla]

I have had my psg1 for 7 years with a 300% spring in it the whole time. I got mine completely stock and did all the work myself. For me the gearbox is very simple. I even custom made most of the parts inside by hand out of stainless steel. So the gearbox being difficult to work on is a myth that got started years ago.
(for the non belivers I have pics of my gear box.)

The part about finding parts is true. That's why I made so many of mine.

The 11.1 lipo will pull a 400% spring no problem and fits in the stock with no modifications.

There are two thing I recomend. Frist get a pdi chamber block. It was the best investment I ever made for that gun. Two words. Rock solid! You will have to modify your body though.
Second, get a metal tapet plate. The upgraded gears will chew threw those plastic ones in like 250 shots.