If I might interject, for the Fattie Piston. Just whipped out 6 of them for a get-together tomorrow. Mine are similar: Schedule 40 Water PVC, 2" -8" in length, Substitute 1 1/4" Schedule 40 PVC - 11" in length (instead of 1" PVC pipe). Glue two 1 1/4" CAPS on the ends of the 1 1/4" piece.
You'll see that the 1 1/4" piece just slides through the 2". I used schedule 40 because I like beefy tools. You'll have to drive over the piston to damage or break it. Unlikely, but if there's a little too much slop on the piston end, wrap a couple layers of saran wrap over it.
While the caps are slightly rounded on the ends, when you push your Fattie material out, you'll be fussing with the ends of the Fattie anyway.
Be sure that the glue you use is something similar to Christy's Red Hot Blue Glue, PVC Pipe Cement. Must be suitable for Potable PVC PIPE.
Final credit however goes upchannel to cowgirl for introducing the idea to us.
~Dave