Flatlander, the windows make a big difference. Especially on vehicles. If they can not see how many people is inside , they might just not attack you. To dark windows attract to much attention. I’ve got buddybar jammer as well – I think it works better on a carpet. The normal rubber (door stopper) kicked nice and tight under the closed door, also does the job. But it is best to have a security door made from strong iron. It depends on the person looking after the keys, how safe that locked door is.
If they want to come in, they will simply break both doors down. But it gives you time to wake up and prepare yourself, if you are inside.