Brilliant solution Jack! This definitely comes under the heading of why didn't I think of that before? Beautifully simple.
I have a question - you suggest angling the seat and not worrying about making it parallel - do you suggest to use the original bolts/holes that anchor the front of the seat rails to the floor? Wouldn't that lead to a 'trapeizoide' effect on the rails that would affect how the seat slides, or don't you think the angle would be a problem.