The main reason I went with the 3" heat tape was that I already had it, but I don't think it would make that much of a difference, especially since I have 8ft of it in there. I tested it last night after I got the heat tape wired and the floor of the incubator was at 90f in about 5 min.
Not sure about the bottles popping open but I know almost everyone else uses water bottles in their incubators so I wouldn't think it would be a problem. Will definitely update as things progress.