Another question, though I'm assuming this has been tried as well - how about moving the spool or another object out of bounds and into a different room and trying to clip from there? It should be possible given that E. Gadd's portals can move objects, though whether or not that's a separate scenario altogether I don't know.

I've seen in the Mario wiki that there are instances of pushing objects into neighboring rooms, but they unload upon switching rooms (most likely as an optimization). So it may not be possible to change an object's "assigned" room without said portals.

Noted. Nonetheless I'll spend some time messing with geometry as well and see if there's somewhere in the area that has been missed - unlikely, but a fresh pair of eyes might turn up something.

Any recommendations or typical methods for clipping through walls short of dropping objects or using moving objects to push Luigi through the wall?

I'm currently attempting a coinless run of the entire game, but I've run into a major hurdle. Old Clockworks C-3 has rafters that Luigi must walk across, collecting coins as he does so.

As best I can tell, the coins don't have physics enabled and can't be blown around, so getting them off the rafter via traditional means is a no-go.

So that leads me to the speedrunning community, given their knack for finding glitches, advantageous or not.

Any suggestions for bypassing these via an out-of-bounds clip, overloading collision or similar?