I really do find the tape works well. Just to reinforce the point - last meeting I hit a wall hard enough for the shock to break the solder between a battery bar and the cells (the cells have been fine for about a year and are well soldered). The pack stayed in despite the fact it was only taped, and i hadn't changed that tape for 3 runs.
Whatever method you use to keep the cells in, if the chassis is filed properly you shouldn't have any problems. Also, if using tape dont get the cheapest stuff (the xenon stuff works well, but a bit too expensive for me. im using much more stuff which works fine).