I cannot argue physics and certainly not something I am qualified to do however I do beleve that head pressure from the full to near empty certainly does change and this is more noticible when a larger tank is used with no increase in suction/muffler pressure from a larger engine.

This became very evident to me when a few years ago when experimenting with various large tank setups for a .45 powered x-country effort, up to fifty ounces.

Since this is the beginner forum I would suggest to anyone that staying within normal protocol for tank size is very good advice indeed.

John