Josh, been thinking about your airplane weight loss question. Sadly, my thinking - not much - given the evolution over the years.


Example -1 One major difference IV to V. Behind the control stick assembly on the IV, the floorboards terminated just past the bungee bulkhead. Yes, in the three point ground attitude, I have had items slide down and onto the fabric below the seat. Solution, design the angled piece that covers the control stick assembly running from floorboard up to the front edge of the seat. This required a reshaping of the front lip of the seat pan eliminating the almost complete "U" that secured the front of the seat to the bulkhead below. Yes, I know of guys that flew many hours with nothing attaching the seat to the tube structure with no issues. With the fairly common incidents of the forward edge of the seat slipping off the bulkhead, the early fix was the straps running below the pan then the blocks between the pan and the structural tubing below. And yes, it was bothersome at times trying to find the washer that slipped and rolled back under the seat. Add the weight of the angled structure and accessories and the hardware (software) to keep the pan off the controls,


Example -2 The typical IV came with no elevator trim. The Speedster came with a trim tab, electric servo controlled. Including ribs in both Horizontal and vertical surfaces for aerodynamics. At about an eleven foot arm this weight did have some effect on W/B, but manageable. Then going to the system that trimmed the horizontal stabilizer with the trim actuator plus the aerodynamic mods that closed gaps,added enough extra weight at the same eleven feet, that a new engine mount moving the engine forward an inch or two was developed. The ring mount is significantly heavier than the original mount. Going back to elevator trim would save some weight, but then the airplane would be significantly nose heavy, so sort of locked in W/B wise.


Example -3 The IV came with tabs welded to the outboard rudder pedal that attached to cables that ran aft just under the outer fabric. At one end or the other - builders choice - parallel strips of steel drilled every half inch or so were placed so that they could be used to adjust the cable length, i.e. the rudder pedals. With the lever actuated adjustable rudder pedal assembly - added weight. Add to that the weight of the center console that mounts and hides all the stuff and it adds up.


Example -4 Most Model IVs were covered with the 1.87 Oz uncertified fabric. an ounce lighter per yard vs. the 2.79 Oz, fabric standard today and - a guess here - likely about half as much polybrush to saturate the weave. Less weight. I know this would be a debatable choice in the minds of most, but the only thing I ever remember hearing regarding the two weights on a Model IV was from the guy whose ftrst IV weighed 604 lbs. empty. His comment was that he learned to like the mid weight cloth better because it resisted the cat scratch tears he would often find as the family pet liked to climb over his shed housed Kitfox at his farm strip.


An aside from talking to the 604 lb. Kitfox guy. We often talked about picking up a Series 7 and then during the build eliminating all the things we never missed while each of use were putting the thousand (+) hours on our IVs.