If you are filling from drum you could still go without a sensor...just tune for something Simple..
For instance e66..= 2 jery cans + 20lt pulp
as long as you carry 2 cans, run it empty put 2 cans in plus 20lts your going to be right.
drove 350kms on pump e85 and figured the tank must be almost empty so filled up with caltex vortex ..iy onpy took 45lt so I was a bit worried ..but mixtures were only slightly lean on cruise..even with some heavy accel it would only hit about 13:1 at worst..i took it to wakefield on this and it was fine. Admittedly my Tune and setup is on the tamer/tolerant side, but it just shows it can be almost idiot proof of done right.