i thank you for your information. it was clear to me when i was on the roof that i really shouldn't be there, but the vents definitely needed covering. i also assumed that the structure beneath me was little more than insulation veneered with aluminum. any plywood would have to be entirely degraded to feel that disturbed. we're tarped over now and intending to begin a rebuild from the inside out any day now. i will investigate your photos and refer to your advice with much appreciation. this dolphin really is an inspiring machine, and crying out for travel. neil