I will have to nicely disgaree, and be a bit different to u other guys on this. If u have to pay 400 bux to get a new backglass, or IF u cant find a replacement backglass for the machine, TAKE IT EASY, I SAY.
It aint a game of strength, its a game of skill. I reckon lock the backglass in anyway.and make sure the head is tied down properly with a head bolt, plus the standard back-catch. After all, these things are very collectible and not cheap to fix if it falls down and something dies/smashs in the process.