scrapes a little on the barrel (tiny bit)
No return spring. (You can easily DIY)
I ordered this pump Kit from http://www.pmpind.com/ on Christmas Day (Monday). That Saturday, I received the pump kit in the mail. It placed in a Priority Mail box, Surrounded By newspaper, with 2 Free stickers :) The total cost was ~$42 USD shipped Via usps priority mail
Installation was Easy. Just pull off the hoses off the "front block" and unscrew everything in the front. Then Remove the Beaver tail, take out the bolt, cocking rod, and the old push rod. Screw in the rod where the Reg in the "front block" use to be, and then screw the push rod onto the grip. Slide it onto the gun, and put the back block on. Put everything back together, and your done!
Just like any other pump cocker kit, it works the same way. Pull back, push forward, shoot, do the same to shoot again.
In the weaknesses, i mentioned that it scrapes a little. Very little, with the stock barrel. This may also restrict your selection in barrels?
To make your own return spring system, simply take a spyder bolt spring, and put it into the grip. If you want less resistance, just cut the spring.
I would suggest getting this kit to convert your Trilogy because it is light, and easy to install.
Its relatively in-expensive. Just make sure when you choose your barrel, you choose one that wont rub against the grip!