I use a 2” PVC coupling to wrap the paper around; and a piece of 1-1/2” PVC with a cap (just slipped on, not glued) for the piston.
That makes a pot 2” diameter, and nearly 3” tall, so their is plenty of potting soil in it, just in case the weather causes a planting delay of a few days.
hank you AG. I’ll see if my plumber has a 2” piece of pvc. He’s already given me 3 & 4 inch pipes he doesn’t want for my garden. He’s a peach.