If you get the WAR one it is drop in after some dissasembly, the diy requires some drilling. Another option is the MBT ( Marauder Blast Tamer ) which is simple to make and installs from the rear end plug without dissasembly, everything stays stock in the rifle. Good shot on the rabbit.
With the WAR SSG the stock hammer you get a hammer with the kit to replace the stock hammer I believe so no drilling.The MBT I mentioned is a different device than the SSG, if you are handy with tools you could make one to try out. Never noticed the difference in sound from the shots, I was paying more attention to the snake. The difference in the sound might be from having the muzzle in the bush.
I think the difference is you would have to drill the hammer yourself.
Or how careful you are. If you have two left hands and no mechanical experience/aptitude or organizational skills, maybe you should get someone else to do it.
I tracked down the instructions for you Victor, here they are. You will like the results you get with the SSG.http://www.gatewaytoairguns.org/GTA/index.php?topic=104406.0