I do it in the vise. Remove the rod and piston. Put rod in the vise with 1/4" piston clearance. Now pry piston off rod. Be sure you have a new rubber "O" ring.
As like rope seals, a small amount of seal above the block allows for crush/tension upon installation. I use a very small film of RTV on rubber seal ends.
I plan to keep my car for a long, long time. And in that time someone will ask how much HP? To answer that question, and for my own curiosity, I dynoed mine. I hate amateurs wild estimates of their HP.