No oil support ring in the 512, just the 499, and it is not a big deal.
Also, short compression height has little to do with overall piston skirt length. Skirt length is really limited by how close the piston comes to the crank at the bottom of the stroke. The compression height can change what ring pack you use and how far away from the top of the piston you can locate the top ring (usually nitrous applications.)
The shorter compression height pistons usually don't need long skirts because the rod pin is pushing/pulling towards the top of the piston, not the bottom. Only the intake stroke where the crank is pulling the piston would make it rock a bit more. On the up strokes (compression and exhaust) and power stroke down, the piston will rock less with the shorter compression height (given the same skirt length.)

I can see where offset grinding a 440 crank and using GM 2.20" rod journal rods would be cost effective for a more budget type build.

As mentioned, 20+ years ago the 451 400 block combination was great because of the low cost, but it basically was a large bore 440 with shorter and lighter pistons in a slightly stronger block.

Now the low cost of stroker cranks, rods and stroker pistons has made these combination quite affordable.

My friend has an older 470" 400 stroker using the Mopar rods journal sizes, but he had to custom order pistons for his application, and that was around $1,200/set?