With back boxes go as deep as you can. Idea being you can coil a little bit extra cable in there so you have scope to easily re-terminate if required or simply want to swap the fronts.
When I say a little extra 300mm or so wouldn't go amiss, especially when try to do the punch downs on the back you have more room.
I’m going to try and get some decent size trunking into the walls. Are there any cable support issues running under floor boards as I see that could be a good area to hide a bit of slack?
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