I currently have a smaller bench mounted 10 ton shop press. It is handy for smaller work and gets used often for bending, straightening, and pressing jobs. I have had occasions when a larger press would have come in handy. The plan has always been to build a larger 20 ton floor mounted press. To that end I acquired two 20 ton jacks, long time ago when the price was right. One for the press, and a second one for back-up.
Now that the steel I need is sitting in storage, I am looking at building the 20 toner in the coming year. The plan will be very close to the 12 ton plan below. I like this plan, it is overbuilt for 12 tons and I will beef it up again, for the 20 toner.
If your interested, there is nice complete step-by-step build instructions here, for building this tough looking little guy.