Rich, I'm thinking of doing the same proceedure with my vintage M17 head. Please keep us informed about what you find that fits. Height will be the critical factor.On the same note, Canadian regulations in the North Channel of Lake Huron call for a holding tank only. Porta-Potties are not legal. That is the only time I have used the stock tank on my M-17.Years back when I had a slip on Lake Waconia, I rigged a plastic gas tank to be my holding tank. That way I could use the marine toilet, but be able to disconnect and carry the gas/holding tank up to the dump station. The marina did not have a pump-out station. Later, Bones (your neighbor in Mpls) ____________________________________________________________ Groupon™ Official Site 1 ridiculously huge coupon a day. Get 50-90% off your city's best! http://thirdpartyoffers.juno.com/TGL3141/4d9144b34846e410123st04vuc