-Think id cut out the tube above WH and just move it up. Is the heater getting screwed to structure members? If so adding a blank piece of tube to screw WH bottom knotching for mount, moving upper header up that much ? Also looking at it if under heater, how is wall getting skinned and still have a uniform surface, actaully at all of the mounts?
On the cieling though with nothing up there not much reason to be climbing but for insulation and spread loads running 1 or 2 1x1s under & tacking to rafters. Could space the rest with wood (not knowing what interior surfacing is going to be) give you another 1" of ins.
Nothing on perimeter of floor at walls?
