Re: Minimum comforts in small boat accommodation.
My Fire-Drake (see Tim Yeadon's video in post #15) has numbers pretty much as you specified in the first post, with a couple of exceptions. The width of the sole alongside the centreboard case for sleeping is only about 460 mm, which is enough for my hips and legs, but mitigating that, for 600 mm aft of the end of the CB case, where my head and shoulders reside when sleeping, the width is 800 mm. The length of the sleeping area is 2160. I have 290 mm between thwart and sole but my height of oarlock pad above the thwart is the same at 200.
For sitting aft when the tent is up, I have about 1050 mm clearance from sole to tent, which gives me about 250 mm headroom while sitting. This gives enough space for lounging, reading and cooking on my one-burner stove. The rest of the tent forward is lower, as you can see, which reduces windage while at anchor, which I believe is important. I don't have angled backrests but do carry a folding camp seat (no legs) for sitting while at anchor. All my gear is stowed in dry bags and then in the water-tight / flotation compartments in the ends of the boat.
Tim's boat has pretty much the same set-up:
This setup worked just fine for for us for 5 weeks last summer and would probably be OK for longer, especially if you pull up on the beach every once in a while to stretch your legs.
"A man who is not afraid of the sea will soon be drowned, for he will be going out on a day he shouldn't. We do be afraid of the sea, and we only be drowned now and again" Aran Islands Fisherman