No, the length of the back will remain unchanges (except of 8mm on the left ower edge to correct uneven lenght)
Just making large holes into the part of the walls of the wheel box which did not get dirty. Like this start - it will be hidden by the cover of the skeleton. Purpose is to reduce weight - more than 2 kg is heavier than useful. If that will be an aerodynamic disadvatage i can still cover the gaps with strong paper (for parcels) which is still less heavy than those 4mm of poplar wood.
