So it sounds like what you are saying is that it was still research and you never actually completed the build of a Sportsman to the point of being ready to fly, and measured the actual finished airplane empty weight?
As stated on the web page, I measured everything from the firewall forward (not including the actual firewall, and I didn't include a nosewheel if there was one).
Is there anything aft of the firewall that would make a significant change in the final empty weight of the aircraft? Without a doubt there are a wide variety of things that would make one aircraft weigh more than another, even with the same engine type installed (tailwheel versus nosewheel, primer versus not, panel item selection, upholstery, etc). You can't compare the final weights of two different aircraft and then determine that the FWF is what is making the difference, unless you know the exact weight of the individual FWF installations. In general, no one knows this because they never measure it.
The whole point of me doing this research was because everyone keeps guessing on weights, and no one had actually measured the difference that I could tell. When Frank removed his FWF and weighed it, I saw an opportunity. I went into this fully expecting that the Subaru would be significantly heavier, because that's what everyone keeps claiming. I was surprised when the Subaru came in only a couple of pounds heavier. So, I says to myself, how can I verify that Frank's weight was accurate? I then made a list of everything FWF on a typical Lycoming installation, and started gathering weights of all of those individual parts. The total weight of all of the Lyc parts came within a reasonable difference of the actual measured Lyc FWF package, so I surmised that the measured weight was accurate, or at least close enough for a reasonable comparison.
As I stated on the web page, it is most definitely possible to put together a Lyc FWF package that is lighter than Frank's. Frank was using a typical heavy, metal, hydraulic constant speed prop, and even just replacing that with a lightweight composite electrical variable pitch prop would make it lighter, and if you custom selected each FWF part based on weight, you could make it considerably lighter.
As I stated at the beginning, this is only one engine comparison, and not nearly enough data to draw any conclusions about the weight comparisons in general, but we definitely can conclude that at least one Lyc FWF installation was about the same weight as a comparable Subaru FWF installation, and therefore possible to have similar weights among other installations. How likely it is to have similar weights is impossible to tell without more data.
-Dj