David, naturally adding these items is going to reduce access, but I have tried to make sure the systems are removable in the simplest possible way.
The ducts on this build are removable by removing 4 x M3 bolts per side, the whole unit slides out from the bypass which has a recessed slot to retain the ducts when in position. The tank 'frame' is fitted by 4 x M3 bolts into blind nuts or nuts depending in preference, so provided the fuel pipes are made to detach this is also not difficult to remove quickly and easily.
I have also added cut slots on each of the two tank formers which will allow people should they wish to remove the x-brace from them to further increase access into the fuselage for maintenance, they do not really get in the way as they are, but the choice is there, naturally these are cut after the formers are fitted to ensure proper alignment.

Hope this helps.

marcs