Gerald,
Interesting work. Your numbers differ from the manufactures by a significant amount. Here are two site that give the Maxcuatro (
https://www.powerpro.com/content/powerpro/northamerica/us/en/homepage/PDP.P-MAXCUATRO.html) (note the line diameters are in mm) and FINS 40G numbers (
https://www.finsfishing.com/FINS40G-p/fns40g.htm). For the 65LB Test line the Max is 0.36mm which converts to 0.0141 inches, the FINS 40G is 0.011 inches. Not saying your method of measurements is wrong but since these are lines designed to be thin and go on reels where they can pack the most line on those reels and the Fishing community is much larger then those of use flying CL they would make a fuss if they were getting wrong information as it misleads how much line they can have on a particular style rig.
However, the exact diameter is really not our concern since we are concerned with strength and drag. Did you fly all the lines you tested? That is where the rubber meets the road. For me the only real advantage of the Spectra lines are you can reduce tip weight and for the same strength as SS lines they are thinner and less drag. The reduced drag for my electric ships allows a small capacity battery pack and significant reduction in battery weight.
I have flown both the Maxcuatro 40LB Test line and the FINS 40G 45LB Test line on the same ship and the FINS 40G was less drag then the Max and reduced amp draw down by 4%. This allowed using a battery pack that was ~1oz lighter then the pack normally used for a 35 size ship. Also reduced tip weight by 3/8oz. That is a significant amount for any stunt ship. For IC's I think you could compare lap times between the different brands to see which one has less drag.
There are lots of brands of very thing and Spectra lines at many different price ranges. If you can do some flying tests and report back on your findings, it will help us all get better performance from our ships.
Best, DennisT