It's not a lot of work to get them fitted at all, as long as you can use an angle grinder and can get hold of a pilar drill to make some brackets. I have them in my car, I have them the same height as I had the standard gti seats so not too high at all. I do know that someone has cut the subframes off of a mk5 and rewelded to the corsa seats and they also said it wasn't a huge job. As for them not being supportive, I don't agree absolutely love them. Plus the price I picked mine up for I couldn't say no to.
Just my 2p worth