My bellows are big also, 4 feet wide and the piston box is like 18" square. Not too far off on some of the measurements I have seen but it works well and not hard to use. I do plan on making one at least half the size to use on a portable setup I would like to build.
First thing made in the new forge, New fire poker. The twist isn't as nice as I wanted because my vice isn't remounted yet lol also recorded it, and when I'm done editing together the video ill post a link.