An in vitro testing process for simulating conditions of a stomach, comprising, in combination: providing an intragastric device to an acetone bath; inducing swelling of the intragastric device; exacerbating weak spots in the intragastric device; observing the results; and estimating the results of an in vivo study. Improvements to an intragastric space filler to reduce failure at a balloon to shaft area including an adhesive fillet, washers, a balloon cuff and collar, a molded in balloon fillet, and a one-piece molded balloon assembly.