Getting about 30 mpg - found that brimmimg the tank created a nasty misfire which disappeared after I'd done about 40 miles.
Have done 220 miles without running out but had been on 0% for about 25 miles (and that was after I'd brimmed it).
Now filling to first click - gives about 95% full but soon goes down and at 0% have only done about 150 miles. 5 gallons gets me back to 95% full.
Seat belts fix would be nice and I regularly wipe the car's bum because it gets dirty at the back where the rear wheel throws up stuff. A better mudguard here - and something to protect the wooden frame from crud - would also be good. Someone's bound to come up with these! I like the hugger idea - this could solve all the issues with muck but is there room without limiting suspension travel?