Last, I just wanted to point out a few really useful videos on youtube by a person called "Daisy880Fanatic" - if you search him out, you'll find them easily enough. Also, here's a curve of fps/fpe vs # pumps for one of my 880s. Have fun!
I have left the power plant and the trigger stock in mine. My trigger is heavy but breaks at the same place every time. I would think for rat, squirrel, and small bird anything out to 25 to 30 meters you should be good to go. I to love GEOs products.
So far the reliability and integrity of the parts has not been an issue at all. However, I think with the added power, I'd expect to have to change out springs sooner. But I've seen absolutely no impact on the plastic parts like the pump arm - I'd actually worry more about a metal arm fatiguing than this engineering polymer (just my opinion).There is a mod for the trigger where you put a small piece of a credit card right in front of the vertical portion of the trigger where it meets up with the sear. Hmm, not a very good explanation. Basically, you are reducing the amount of trigger catch on the sear by taking up some of the space. If you search this forum for trigger mod or maybe credit card mod, you'll find it for sure. Maybe someone else has the thread handy?