Post Driver for Sand Point

I would like to make a post driver for every one I have seen is light weight. I was going to use a heavy wall 2.5" ID pipe and have 1/2" handles installed on it. The head of it was going to be capped with a 1" steel round plate welded to the pipe. I want to make sure I am heading down the right path, weight, ID dimensions to fit the drive cap etc. Anyone can help it would be appreciated. Thank you

Thank you. I end up making one. 24" length, 3" id type, 1" heavy walled pipe. 3/4" striking plate, 9/16 round handles from top to bottom. Come out heavier than what I wanted. 60lbs even after we lathed some of the pipe down!!