That's sound exactly like what I had in mind. I have several unused concrete silo staves I planned to lay across the angles and then strap down. I know that steel scrap would weigh more, and that original Allis weights would look nice, but the staves are free and nothing can beat that pound-to-dollar ratio. Are those threaded holes in the frame 5/8 inch? I tried putting a 5/8 grade 5 bolt into one of them, and they seemed to mismatch just enough to round off the bolt threads. Thanks all for your suggestions, it sounds like this idea will be safe, if not elegant.