Shock mitigation is tricky in a SIB without the ability to have a jockey seat position a la RIBs.
I know some people like them and they might be
OK on rivers but seats on a SIB don't work for me and I find the best idea in terms of comfort/safety/control for typical UK F3/4 seas is the standard RNLI taught SIB position so kneeling on the cushioned floor (use closed cell knee pad) with LH on tiller, RH on SB tube grab handle.
If not too bad then piloting from sitting position on SB tube with hands as above. But do an hour or more of this and your spine takes a beating which you'll feel the next day.