Portable ramp for scooter - what length?

[Twende]

Actually this is going to be on the side door of a van.

I am leaning towards a 4 foot ramp. Just don't know if I will regret it and wished I went to a 6 foot.

You could always get a board and see how it fits and then get a ramp the same length. Or even get a large cardboard box from a frig or freezer and put it int he place of the ramp and see how it looks.