I've done a LOT of load development with .45 Super, running it in several different platforms . I've not used it a lot in the 1911 so far but I have plans to do more. That said the .45 Super (btw 450 SMC is basically a small primer version of the .45 Super) you get from Underwood or Double Tap is very similar to warm 10mm ballistics, so I would think spring weights for those loads would be very similar to what 10mm guys use in their 1911's.

I would probably get at least a 24lb spring and go up from there just to test out, see which one works best. I have a 28lb I'm plan on testing out. I did run some mid-level .45 Super through a bone stock 4.25" Ruger LWT CMD (250gr @ 1050 fps), but it needed more spring. The fullsize 1911 will benefit from the heavier slide, so coupled with a beefier spring it should handle the mid-level loads just fine.