Hi folks...
It took me a really long time, but finally I managed to realize a custom that I already have in mind since a long time.
The new plane has not - as the old ones - a storage compartment in the end of the plane, so there is a large unused space...
...so here is my suggestion of how to use it.
First, I put out the last cabin wall, which is sealing the empty compartment and drilled two holes, one for a 9V-block holder and one for a small switch.
(I drilled a little gap for cables, but did not use it after all...
)