Earlier this year, I noticed that my door is not closing properly. I found that the upper hinge is tearing loose from the door. I'm not carrying the spare on the door at the moment until I find a fix for the hinge problem. I'm pretty sure that the door can handle the weight if a wedge is placed under the door while closed to limit the bouncing that would occur.
Of course for all I know the door & hinges were holding up fine but something happened to it while the door was open one time.
I just haven't dug into it yet to come up with the ultimate solution since I can't run around without a rear door. I've got vt_maverick's old door now so hopefully I'll get started on it very soon.
Yer right though, the cover won't fit with anything larger than the OEM donut.