I have seat heater elements that need to be installed, but I've already installed the floor boards into the cockpit. So, the short answer is take them out. Not such an inconvenience, since I had already decided to do that because I hated the floor color I chose--white doesn't really work.
So, I went about the task of removing the floor--drilled out the rivets and popped it out. I laid out the wiring harness for the seat heaters to get an idea of where to route the wires. There is a sealed junction box (I guess) for which I fabricated a bracket and mounted it one rib inboard of the copilot right seat belt bracket. I RTV'd the box to the bracket. I routed the wires through cable clips and snap bushings through ribs. The passthroughs in the floor are drilled large enough to pass the plugs which determined the grommet size I used for the holes. That worked out well, and I located the plugs at the back of the seats near the seat attach points.
I routed the fat supply cable forward to the aft side of the spar box and then on to the center channel where the cable joins the rest of the wire bundle heading towards the instrument panel power buss.
