I've just spoken to Exmoor Trim (who weren't answering their 'phone over the weekend).They say that the flip-up seats shouldn't have the same problem, since they're smaller, sit further forward, and have a thinner back. So, I'm now pondering whether to get two flip-up seats, keep it original with two new benches, or go for a Tory Blair style Third Way by fitting a flip-up seat on one side and a bench on the other. (I have an LPG tank in there which takes up too much space to fit two individual seats on the same side.) Thanks for the info/advice.