great advice on here...
I have a 3.8 sib and 20 hp Yam as well as the SR4.
I learnt so much from running the SIB that it really helped when I got the SR4, particularly with reading the wave action.
Relatively smooth conditions can still be really bumpy in a SIB at speed.
Pay attention to wind / wave direction tides etc... a smoothish run down the coast can turn into a bumpy wet slow crawl back into a head sea, even when
running diagonal to the waves. Confused water and short chop is even worse.
BUT a tiller extension also helped when by myself in the SIB for getting weight forward. Sometimes you just have to slow down. The big Ribs handle it easily, but they have to stand off a beach when you can run the SIB right up on it.