This is very analogous to people saying that training can’t change your VO2max by more that 15%. 15% is a huge change!!! As is even a 10% improvement on frontal area. I’d certainly take that!
No, it’s really not analogous at all. He’s right, FA is overrated–and any resolution greater than looking in the mirror is pretty much a waste of time.
I would use it in conjunction with other measurements, of course. But for me, anything that drops FA by more than 3% is always worth investigating. YMMV
Consider this: Indurain’s FA in his TT position was roughly 15% more than Rominger’s FA. If you’ve ever stood next to both of those guys, you’d realize that’s pretty startling. So, differences within the same individual, once you bend over a reasonable degree, just aren’t that much, more like a percent or two. Also, remember that FA is typically half of Cd, so a 5% difference in FA (which would be huge within the same individual) could be offset by a 2.5% difference in Cd (which isn’t that huge).
Since the relevant parameter is CdA, the product of the two, how could 0.95 * 1.025 ( = 0.969 ) not be beneficial?!!
Ron’s comment regarding Cd being relatively fixed is inaccurate as well. For some riders, doing things which increased FA (such as moving the arms out wider) can decrease Cd enough to more than make up for the increased FA. Similarly, sitting farther back on the saddle and raising the front end can have a positive effect on Cd (by changing the orientation of the upper leg to the wind), all while increasing FA–but with a net decrease in drag.
Ron’s a pretty smart guy. I’m sure when he says that it’s “relatively fixed”, he is comparing it to the “relatively changing” FA.
Bottom line is that using FA measurements to this degree of resolution doesn’t have much utility. People like numbers, so it’s easy to say "my FA is “X”, and lower is better; but lower isn’t necessarily better unless you know how those changes affect Cd…and a pixelated photo isn’t going to give you that information.
I’m pretty sure I can use the info. And any person versed in aero field testing can greatly benefit. Again, YMMV.