Why do I have rust here, and does it matter?

[scoot]

In the DIY restoration of our car, we have found some rust somewhere unexpected.  We have re-painted the hardtop (without removing the headliner) and in the course of reassembly (putting in the back window) have discoverd bumps of rust under the upholstery that covers the panel just under the rear window.  (see photos).  I don't understand why there would be rust here since this is not a low point where water would collect.  The only way I can imagine water collecting at this points is if there hardtop were stored upside-down and it got wet, which is entirely possible. 

Any ideas as to why it got rusty here?
Any thoughts about whether it is worth fixing?

thanks
Scott

[Garry]

Scoot,

I have recently totally stripped and glass peen-ed my hard top that had the classic rust spots on the lower left and right hand outer rear surfaces and also some rust in the inner corners of the rear glass. There was no rust in that area but I stored the top flat. Other than those common areas for rust there should be no other areas that rust would normally be.  I would suspect that your hard top has been kept in one of the rolling stands with out a cover rather than hung or laid flat allowing for either condensation in cold climate or water from another source to pool at the bottom .  I would suggest removing the rust otherwise it is only going to slowly continue to rust until removed and re paint the area.  If you use the stands, always put another cloth/cover over the whole stand and top as they will attract condensation if it is getting close to freezing as often happens in a garage

[al_lieffring]

Scott

have you peeled back the covering to see if in fact the bumps are caused by rusting?

There are other posibilities. like the surface wasnt completly cleaned off before the leather/tex material was replaced.

[scoot]

have you peeled back the covering to see if in fact the bumps are caused by rusting?

Unfortunately yes, it is rust.   :-(