I don’t have the answer on how to test the float, but do have a suggestion for you. When you are reassembling everything, put a dab of white paint about 1" from the ends of the connecting points on the tanks and the cross-over tube. (I am just guessing the 1" measurement from memory, but the exact amount should be pretty obvious once you install the tanks, lay the tube in place and hold the connector hoses in place.) The hoses are a bear to get to slide far enough up to seal completely and too thick to be able to feel how much they are over the pipes. That drop of paint will give you a good indication of when enough is enough and prevent leaks.
Oh, and is this the rubber connectors you are looking for: http://cgi.ebay.com/ebaymotors/Sunbeam- … ccessories? If so, they are readily available from either Sunbeam Specialties or, as in the case of this auction, Classic Sunbeam.