Appowner - While I am tempted, this is not my own aeroplane and the owner do not have too much cash to spend on it. I will be doing the repair work within these limitations.

As mentioned before, the bottom of the fuselage covering was "held by tape" and of inferior covering material, which raise suspicion that some damage was covered. It was easy to spot one area of concern as shown in the photos. I used a torch to look to the back, and had to remove another tray that was interrupting the investigation and was not part of the original aeroplane anyway. Considering the amount of additional led weights at the firewall I am confident that additional weight at the back will not be needed.
The owner was not sure which batteries he will be using, so I made trays for both NiMh and LiFe and located them as far forward as practical for easy removal.

Cheers,
Eran