Technically the flange is only to stop the wheel face from slipping off the head of the rail with the Tire riding on a very narrow strip providing traction.
Providing you only propose to travel at a walking speed you shouldnt need too much of a profile of the tyre/flange but speed up and you'll soon find it will derail, even on a straight.
The 3 wheel Pull 'Trikes' were notorious for getting the outrigger wheel out of alignment.
Riding on long sections of welded rail is like roller skating on a rink but on older smaller 30 foot rails that have been 'crowed' to make a curve and where each rail joins is a potential hazard if the wheels are not correctly aligned and in good condition.
One afternoon many years ago I rode home with a rerailing gang on a 3 man each side seating one cylinder water cooled 'Fairmont' engine gang car between Brewongle and Locksley at an unknown (but BLOODY fast) speed on newly laid welded rail and it was FANTASTIC !!!!