decided i'd share this i have no idea why we didnt think of this setups pretty simple:

1. go to L4-D3 w/ the coin door open and one key left
2. touch finish checkpoint
3. grab the remaining key, you should get onto L4 end screen normally
4. press next level (and maybe wait a bit like i did, probably not needed)
5. you should instantly beat L5

in the off chance this does NOT count as a prerun setup then level 5 any% glitches ILs are doomed

see the following for further details: