Posts 18-20 make many points that were missed. Like most
multihull sailors, he will be
cleaning while standing on the bottom.
In this situation (I've had 3 multihulls), the only down side of a dry suit is cutting it on
barnacles. You'll just have to be careful. You should be
cleaning before there are more than a few. If the water is truely near 35 F and you are worried about the shock of cold, this is the way to go.
No, not
cheap. Used dry suits are likely to leak.
As for latex allergies to the
seals, you can probably fit something under them. Nitrile gloves. Maybe a very thin balaclava over the neck. It will leak, but your
head won't be going under much and the balaclava will keep critters out of your ears. I would ask a drysuit maker. Get a suit with attached feet (no ankle seals).