Kbrosmith,
Most cobra owners have some issues with motor mounts due to excessive engine torque over a standard driver. My 427SO, only after a short time required the mounts to be replaced with ploy-mounts. This has nothing to do with the cobra replicia you have.
I have my car for about 8 years and have had no problems with doors, hood, or the trunk lid. Never heard of any other Superformance owner say anything about their doors comming loose, this is the first. I have found the Superformance to be a very stiff framed and well made for the money replicia. Their were other choices, but in the end it was the right choice for me. IF you would like to see mine or talk, call me @ 717-733-4786 owner of the "Mistress" SPF1425.