I'm measuring up with just the same thought in mind as I'm planning to fit a rear pilot's seat to the Aerotec which is only fitted with one forward for the passenger. I've been trying sitting at various heights to see what is comfortable. It looks like I'll be fitting my new seat a little higher than the standard one.
I also plan to get these cushions which are designed to give extra height to SIB seats...
https://bengar.de/en/polster-sitze-s...boot-55cm.html
You could easily achieve similar height gain by making a false seat to sit on the existing one with a timber frame of a thickness you choose.
Alternatively if the SIB you chose had seat mountings anywhere part way down the tubes you could fit another set of seat mounts higher up and make up a DIY seat to span that wider dimension.
Of course you could just sit on the tube which gives the greatest height and leg stretch possibilities.
Perhaps folks who have their SIBs inflated at the moment could list their floor to seat heights? As a start... the existing Aerotec one is 35cm and the new one I plan to be 38cm.