Well, I have a Corse Slipper in it so bumping it would be an issue even if I could run - which I can't because of my ankle. Not taking into account compression issues.
I haven't tried jumping it off the car yet - I'll do that in the morning if it doesn't start after being on the optimate all night. I left it on the optimate for an hour and it turned over a bit but wouldn't catch. So I'll leave it until the morning and see what happens.
Bloody thing!