Bob - I have done all of what you describe on a -9, but the -4 I am building is not yet at that stage. [ I was going to take the wire inside the fuse through the big hole in the deck between the two spars. You just need an Adel clamp to make sure it does not chafe on the edge of the hole.
The under the floor route would be great but how will you get past the main spar? I was thinking you would have to come up one of the diagonal bulkheads and then continue under the rail above your elbow. As you say crossing the rudder cables will have to be done with lots of care. You could also stay up by the main longeron the whole way but the bulkhead by the passenger shoulder is a messy place to pass neatly.
Steve,
On the wiring, if you go down through the main inspection hole, you still have the elevator tube right there in the way and you still have a double bulkhead in front between you and the open fuselage. That was the reason I thought of drilling that small hole through the 50 mil splice on the front horizontal stabilizer spar. That hole would be just behind an existing hole in the bulkhead right above the fuselage longeron. You would then have a straight shot into the fuselage. You can use the existing 3/16" holes in the inner rib of the horizontal stabilizer to route the wire without using adel clamps provided you put RTV around it to prevent chaffing. (I believe that is acceptable??)
REgarding the main spar. You will have to cut some of the thin webbing away on the main spar at the center junction so the control column can pass through that double bulkhead. I am told (someone verify please) that the web in that area is not a structural item and must be trimmed to make room for things like the control column. I so no reason why a small hole for the wiring will be a problem. I need to hear from others about this before I do it.
Regardless, I appreciate you information and I will be looking at it and for more and perhaps we can all benefit from it. Thanks.
Bob Mears