I recently started using MyWindsock premium (US$15 a year) as an addon to my Strava. It gives a CdA calculation to rides on Strava automatically (if you ride with a power meter)... so much simpler than loading data into other tools that do this. It also seems to be pretty consistent. I like it so far. Might be a good tool for those wanting to make their Vendetta as fast as possible!
Anyway, I am able to go through some history of riding on the V20. Unfortunately recent COVID restrictions in Sydney have prevented me from riding some of my faster riding loops. Just before that restrictions, I did two rides on my fast loop with the only change being going from my OEM V20 wheel/tyre setup to my Roval 50mm carbon wheels with tubeless tyres. This loop is around 80kms with a 20km section by a major motorway with wind assistance from passing traffic (large island between traffic directions, so only near vehicles going in the same direction) which probably enhances CdA calculations. Old wheels came back with 0.166 CdA. Rovals with 0.147. Unfortunately I was unable to continue any testing on this loop after that. My new loops are on lower quality road surface, and more hilly with less traffic related wind. At the same time as I started riding the new loops, I fitted the Brain Box bag. This is quite a large bag, and I am quite short, so in my case, it is higher than my shoulders and exposed to clean air flow (even with the bottom just above the tyre). The brain box did allow me to remove the under seat bottle cage which was also in clean air. On the new loops I am getting consistent CdA in the 0.17-0.19 range. Probably variation due to changes in clothing and weather. Unfortunately I cannot determine if the increase in CdA is due to the change in riding conditions or due to the addition of the brain box. I will test this at some point when restrictions are reduced.
For me the Brain Box is much larger than I need for normal riding. I think it is a good size for long rides that may have variation in temperature and I would then need to carry clothing, so I am glad to have it (can fit in 10 minutes). But normally when I ride it is empty except for my hydration pack and my phone (I have the moose pack for my tools/spares). I would like something smaller that can carry a 1.5L bladder and not much else, but completely out of the clean air. The race case looks like it hits the mark, but for me in Australia, the CB website is quoting me >AU$500 delivered, which is very expensive (the brain box was <$100 delivered). Has anyone farbicated a nice rear pack that is aero and can just hold a 1.5-2L bladder? A nice quality off the shelf bag like the brain box but half the size would also be good. I do prefer soft case options over hard options that rattle and are more likely to crack/break.