DIY press

In the process of trying to decide oh metal parts for my press, have most of the other items. I was deciding on how I want to do myframe. First thought was 3/8" or 1/2" all-thread, but then started looking at like 303/304 stainless round bar since I could cut my own threads in them. I know round bar would be better for smooth movement of the bottom plate.

Which would you use?

Also building my own cause I need a compact footprint (all I have is a room in a house, so I have to use/store it...

DIY press