Our shooter/hopper took ideas from Ri3D as well as some things from 3847's shooter.
However we used our own implementation as well as added some of our own "twists" and improvements. And yes, those are the 2-7/8" x .8" blue BaneBots wheels. As far as compression goes, not quite sure as we didn't measure it. Our motor carriage is adjustable so that we can tweak the compression as needed.
Although after about 250-300 shots we seem to have finally worn out our shooter wheels on the secondary (throwing) wheel.
We are also doing a pretty good job of throwing them upside down.
http://youtu.be/wAFUmm_C-KE
Another addition is that we have the ability to tilt our shooter from about 30 degrees to about 70 degrees. At the highest tilt we can stand about 2 or 3 feet from the high goal and still score in it. Our biggest problem is that the low goal is the hardest to hit. LOL