You could do it either way. I ran mine after I had the floorboards, etc installed. Slightly painful but not too much drama. Some of the heat shrinks are in just the wrong place and interfere with grommets. It would be easier to reposition them if everything was exposed. Also, Iím sure running additional wires for extra goodies would be easier as well.
Not sure if the harness would interfere with riveting. You may want to check that.
Carrollton, GA 5GA2
RV-14 - Hoping to fly sometime this century. Almost done.