I didn't think much of the beams being welded together at the time, but it turns out I should have. Here's what happened in the first inflation:
It peeled the top plate off the end of this beam like a tin can. Upon inspection I realized that at the beam end that separated, the weld stopped short of the beam's end. All of the welds are only on one side of the web, instead of both... if I could weld I'd change that. Luckily, the weld on the other sections were better, and the other side has held up to 85 PSI with the aid of 10,000 lb tiedowns, for a little extra precaution (or so I think, at least):
I posted this in hopes that someone buying scrap steel doesn't make the same mistake I did. The steel would work fine if the welds had been done properly, or just minimally reinforced. I feel silly not considering this when I bought it, but everything is easy in retrospect, right? Good thing I wasn't using the whole press, so we still have a functional half side.
I am also selling this press, because, due to circumstances beyond my control, it can no longer accompany me on my move in two weeks. If anyone around Tahoe is interested, I'll post a detailed ad with specs in the Yard Sale section. Half of it works great, and I imagine that minimal metalworking skills could fix the bent sheet and make it into a two ski press again.