Another Human Power Thread - Monohull, Cat or Tri or something odder?

Before I set saw to wood, I thought I'd have one final plunge in the deep end of boat design just in case there's something I'd not thought of. So here's what it's for and what it'll have to do.

It's being built initially for a trip the length of the Nantes - Brest Canal in France. The Nantes - Brest is made up of five canalised rivers with 3 short 'biefs' or linking canals. The canal is 360+kms in length, there's 280+ locks of which only about 170 actually open, the rest have either been sealed, or have rotted away. In some cases there are weirs with kayak slides (1 metre wide) down them which could be usable, in other case I'm going to have to pull out and drag/portage round.

For preference I'd like to be able to live (well sleep) aboard some of the time. A most of the canal is very little used (and then only in the tourist season) and no navigation is allowed at night so I'm not likely to disappear under a 200 ton barge. Also whilst none of it is remote, because of its lack of use there are plenty of places where campsites/b&b's/hostels just don't exist, and the surrounding land is very marshy, so being able to bed down aboard would be a big plus.

Finally I'd quite like a closed or closable cockpit as there's plenty of dull wet days to be had in Brittany, and 6 to 8 hours of pedalling in the drizzle isn't going to be a lot of fun, and even more finally I'd like it to look a bit different. Part of the plan is to raise money for charity at the same time, and I even have some fools prepared to pay for me to put a logo on the boat, so if it's eye-catching, it's media grabbing, all of which helps raise more cash.

Thoughts so far are:

A 6 metre, 90 cm beam monohull, centre cockpit with sleeping quarters (or maybe eighths) astern. Foam core, fibreglass with a very very lightweight 1mm flexible PVC sheet super-structure. Easy enough to build, should be reasonably lightweight, and it'll fit down the kayak slides, but damn cramped if it's pouring down and I don't feel like pedalling much, and also a bit tippy.

A 4 metre, 180 cm beam catamaran, centre cockpit again but with transverse sleeping quarters astern. Foam core hulls again, and super-structure similar. Bit more difficult to build, bound to be heavier because of the cross beams, and it won't fit down the slides so I'll have to portage, which with a cat will be awkward, but the accomodation can be bigger, and better suited for lounging round in (haha) with a book.

A 4 metre, 180 cm beam trimaran, construction pretty much the same as the other two, with 2 metre amas astern. They'd be such that in cruising mode they only just dip into the water, providing a bit of stability, but when moving astern to sleep they provide increased flotation, and stability. Their hull shapes would be stepped or fairly shallow V to cope with the change in weight distribution. Almost certainly they'd be removable from the centre hull, and could even have enough bouyancy to happily float on their own like a pontoon, with me aboard (hey just like having a campervan attachment for your pick-up). A fair bit more difficult to build, again bound to be a bit heavier (for the inevitable portage, although I could separate the bits. but the accomodation can be bigger, and the two crossbeams for the amas can straddle the shallow sides of the kayak slides. Also it'd look very odd, maybe cool, and would certainly attract attention, which hopefully equals money.

All of them would be prop drive, rear mounted prop on a swing arm (think inboard, outboard).

So can anyone think of any more ideas, point out any big problems, toss coins, whatever, before the saws come out. I'm taken by the Tri, but at the moment would probably build the Mono, but hey I'm easily swayed by a convincing argument.