Placement Rounding Errors

So this is only really notable with the really huge ships.  So the best example I have of this is working on my latest exercise in excess an orion drive powered super cap ship.  I use cone based set up to make the ships almost impossible to pen frontally due to the sloping so I place most of the hardware in the rear section of the ship.  As such I create the rear section first with all the radiators and other hardware.  But once I have the radiators all set up to remain hidden behind the frontal cone I start to add on 100s of meters of length to get the slope I want.  BUT once I start doing that the rear most radiators on the very end of the ship start to freak out and stop being attached to the side of the ship and instead try and fuse with the engine and even when I try and use fine movement with the mouse it doesn't really work as now the movement steps are larger as the ship got longer and for some reason which I think is rounding issues I can no longer place radiators as close to the rear of the ship.
Example this is how close to the rear I can place a radiator with a 1.5km long ship:

This is how far down I can get with a 2.5km long ship:

These ships are identical in all ways other than length which is why this is so annoying.