It doesn't look super tight to me as it happens. If its 4ft high, then hopefully it has 8ft of flat bottom. If that is the case then it would ride like Roms wooden mini that is over by the clover bowl. So not so bad really for a back garden ramp, nice and quick.
But its way too narrow, presumably 12ft. You'd have to extend it at least another 4ft, and preferably more