Apologies for the lack of measurements, I’ve come down with something nasty (probably just man flu

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Reading back I was being a bit silly suggesting there’d be a difference in the measurements since it’s the seatbox that’s sloped as opposed to the the actual cushion, so the distance to the top of the cushion from the seatbox should be consistent no matter where it’s measured

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Looking at the picture you’ve just attached I’d estimate the normal basic seats are about half the height of your current seats, I’d also hazard a guess at them having a lot more give than yours too.
I agree with what grewth said in finding one to try out, but with that said I’ve just done a 250mile round trip for the Land Rovers of London Christmas meet. What I found was that if I forced myself to sit with my knee in line with my hip instead of what I used to do which was to ‘manspread’ I tolerated it much better with a lot less pain. Key word being less though and not completely gone