Dennis Thanks for the erudite reply. Experience trumps speculation every time. I did label the external tank speculation as fantasy, intended to both stimulate discussion and perhaps spark innovation. My personal speculations about modifying a sailing catamaran did not involve disabling the sails in any way, only expanding the tankeage to provide longer range under power, at the cost of internal accomodations (the Admiral and I don't need four staterooms usually found on the boats coming out of charter service nowadays). We met in Poulsbo in 2003 -- I was in the little PDQ34 parked behind you, and I want to thank you again for the gracious tour and stimulating discussion we enjoyed then. Cheers Gary