I don't think condensation will be an issue when it is not sealed and the box is all plastic. The electronics get warm so even in winter would dry out if they had got damp, but from what I've seen even after driving in cold damp weather it has...
I spent hours looking for an enclosure the exact length and width I needed for the main LV JB but there was nothing that suited.
The new extension is even more oddly shaped due to the slope of the bonnet so it suits better to have made them...
I guess you probably know about these anyway, but I'm always amazed at the range of off-the-shelf electrical enclosures that are available. RS have a similarly huge range too - and of course, as many waterproof cable glands as you can shake a...