Kind of interesting discussion on this. I’ve always found it to be a try it and see, and adjust if possible. After recently acquiring a very early Phil wheel set, this is something to look into. OLD on this set is about 120.8. The distance from the back ledge for freewheel to the locknut on this one is about 32mm. A five speed freewheel has way more room than on nlerner’s hub with about 5mm to the face of the small sprocket. Two compact 6s have 3.5-4mm to the sprocket.
5 speed
Compact 6 on perfect body I think
Compact 6 on pro Compe body
Just a few data points for anyone interested.