I've been reading this thread with interest for a few days and despite understanding fully where Ken is coming from as someone myself who's SIB is their only boat I'm leaning towards Steve's advice.
My thoughts are somewhat in line with the last couple of posts from daijinks.
I have a 9.8hp 2-stroke that weighs the same as his excellent 8hp Yamaha and previously owned a 4hp as well. The 4 and 8 aren't worlds apart on ease of handling unlike going from these sizes say up to a 20hp. And a 3m ish SIB isn't that much worse to handle both packed and inflated than a 2.4m. So I would sell the 2.4 and 4hp then put those funds to the money you were going to spend on a used SIB and but a new Boatworld 3m V air floor, Honwave style/design but cheaper and 99% as good.
Decent price at £795, looks nice, Boatworld are decent guys to deal with and it only weighs 32kg which is so easy too manage.
https://boatworld.co.uk/boatworld-air-v-type-floor-300