I’m all for the “drop the feet and lay it on a 1/2” MDF + thin foam", just remember to make a few pockets on the MDF surface where the feet used to be as well as in the various places where the welded nuts protrude from underneath the steel frame. Below is my example (for a small SO3 and while installing an aluminium bed, but the principle applies)
There are also a variety of options where people just added extra adjustable feet under machine/wasteboard. Here’s one example, I can’t seem to find the one I had in mind but it is similar: threaded insert installed on the middle of the bottom side of the wasteboard, screw leveling feet into that, adjust height to compensate for sag, done.