For me (please forgive another intrusion in your thread, craig), the arm closest in my photo (looking from the front of the model) interferes with one of the mounting pegs for the hold base.
Also, the step up at the end comes up a bit high and hits the hold base.
My thoughts: the peg could probably be removed and another support added elsewhere (if needed). For the step up, I thought (maybe) a section could be cut from the hold base the step could go up into IF the step could still fit under the floor.
Another way is to fab (not by me, lol) a one-piece, flat arm with a notch in the side for the peg, replacing just that one arm, or all four.
So, more to plan, but I'm sure it's going to be possible.
What have been your findings, craig?
EDIT: The base only needs to go a tiny bit further (red lines). Notching the base enough to go down should still keep the step and the bolt under the floor. The spacer is 0.50".
Here is the stock arm with the notch cut out of it and final outcome.