I keep mine together then lay them out in the wheel house when not on the boat. When we are on the boat they all go in the roof mounted holders and in the gunwale mounted ones too.
like this...
and this....
Neither will this. I'm replacing decking that we laid 15 years ago. So that's not a bad return. For the cost of the deck boards I can do this twice for the same cost of composite boards. We are using concrete this time to stop the supports rotting and wicking up to the boards. If we do get some rot this time I can just replace individual boards.
Cross beams have baton running along, then the deck runners are notched out to the size of the baton, laid on top then nailed and glued in place. All mounted on concrete posts
2 stroke offers a lighter engine to hang off the transome with more power. For an aux I'd go 2 stroke all the way. Either way, Tohatsu is a good choice.
Don't suppose your self employed Jon?
If so, you could always get a new Tohatsu 2 stroke as an aux engine. I did it, got a new 5hp 2 stoke for my tender, think it was £1200 iirc.