Thanks for the feedback Robert. I will say that further disassembly of the cab and interior is not particularly appealing to me right now
I do however think/wonder that an additional clamping method could be worked up using j-hooks or a similar small clip. Attaching a hook to the back panel lip, that the new panel lip could "slide under" after applying the metal bond, would help provide some actual clamping force, and a mechanical attachment that would prevent lift or at least reduce risk that the bond could break over time. I recognize this is not by the book or per the instructions of the panel bond, however it may be practical.
I may also start a dedicated thread on this topic in the main section due to the low traffic in this forum, and how this topic has shifted from the original thread intent. The fact that this panel is reproduced means there are at least a moderate amount of people performing this repair - surely there are a few more lurkers here who have done it.