I'm thinking stick w/ a hard bottom paint.  If you are in an area where copper paints are outlawed, try one of the slick teflon racing bottom paints that you can wipe clean every week or so with a sponge (if you wait too long you need a lot more elbow grease).  If you can use copper paint, Baltoplate is what we used on the racing boat.  Paint on several layers then fine sandpaper and even a bronze wool burnish to a smooth shine that still has enough copper to provide some antifouling. And it is a pretty cool bronze color. It's a lot of work for a 30' keelboat, but should take very little time for a NED.   Still need to clean every few weeks but that's not much work for a small boat you can drag up, wipe with a sponge and toss back.  And it should be fine out of water.  For a winter- hauled boat, if we had enough thickness, we'd just resand it lightly to expose more copper before splashing again.  All of them are ok in the sun.  

The ablative paints are not what you are looking for, and some environmentally sensitive locales don't like them anyway because they continually shed paint/copper into the water.  

Have your cake and eat it, too; build a second boat--one for the mooring, one for the cartopping, each with a bottom appropriate to its use.  In fact, the cartop boat might be a different, perhaps lighter, sort of craft altogether, especially if sailing is less important in your mountain lakes scenario.  <;-)

.....Michael

My Skerry is moored 20 metres off shore from May to Oct/Nov and our local beach is rocky with some very gritty coarse sand. I painted to bottom to suit this fairly harsh environment. On top of the epoxy fill coats there's two coats of epoxy barrier coat. Now I don't know what your going to call it in the States - I live in Southern Turkey but it's basically a very tough epoxy paint. On top of that is undercoat and the normal hull paint then two coats of antifouling. I took the boat out of the sea last November and the bottom was clean with just a few scratches from the beach.

I should have mentioned that there's two coats of undercoat for the antifouling paint! There's a fair bit of stuff on the bottom of my boat!

Josh,

Last season, my Peeler Skiff changed from being trailered to living on a saltwater mooring from May through October. I ended up sanding off most of the Brightside from below the waterline and painting the bottom with Interlux Fiberglass Bottomkote NT. It's reasonably hard and kept the bottom clean for the whole season. Looked new when hauled in October,

The entire exterior of the boat is sheathed in fiberglass and epoxy resin, so Fiberglass Bottomkote was a reasonable choice. I do not know how the bottom of your NE Dory is coated, so I don't know how appropriate this would be for you. It comes in black, red, blue, and green.

Cheers,

Dick