First it has been many years ago since I made it so this is close,
All the cutters have a bearing guide on the depth of cut,
It is one shaft, I think there is a shoulder on the shaft 1 shaft turned down to 3/4" and threaded on the end, is my guessing with out going out and measuring,
The cutters are stacked on using a number of spacers, and the non pulley bearing is clamped in as well, with a nut, and the other end is just locked in with the eccentric locking collar, locking the eccentric collar down after the nut was tight,,
The frame is (need to go look again, I will edit the post when I look later to day) the sides are 1/8" x 6" spaced with a angle iron, looked like 1 1/2" and the ends I think were 4 flat
the legs are angle iron,
The fences are wood on each end of the box that holds the shaft are two angle irons, top lip slotted the long way, other lip slotted vertical so the fences can be aligned to the cutters, all of the fences have a floor in them, that the product slides on that is nearly in line with the rub bearings, if one wanted perfection one would have to shim the ends of my fences, (one could make three short angles for individual alignment, I think I used Reversible Stile & Rail from Grizzly,
C2314 Reversible Stile & Rail - Roman Ogee w/ Rub Collar, 3/4" Bore
On the end cut there is a sled with a clamp, that rides on the fence, and part of the trick is to have a back up (which is attached to the sled holder) so the ends do not split out,
I have set it up once and have not, changed the setting or the cutters,
personally I think if I really wanted a different profile I would make a new machine, or if I wanted more panel cutters, may be make one with all panel cutters, in it,
(now the RBI panel master claims to be able to run arched doors) my fences do not have that kind of adjustment and would think one would need a shaft for a starting guide on the cutter), when I have made arched doors I will set up the arch cuts on my shaper, really I do not think if I was rebuild or make a different machine that using end pieces that were lower one could make arched on the machine with a different guide fence,
If you have more questions, post and I will check back pm me if I do not respond I may have missed it,
I added pictures to show more of the constuction and the cutters and the rub bearings, hope this helps,