I thought I recall Grill make a comment on these forums that his position tested differently on different frames. Something about his old Plasma position replicated on his P5 tested differently.
What do you think? Or would the ability to test so many positions so quickly 'probably' be an ideal position for whatever bike the tester is on?
Yeah, I don't foresee that being an issue. If you want to tease out those numbers, you'd need multiple tests on multiple frames making sure everything is replicated to the millimeter. Those clients are basically non-existent, and even then it would be a mostly Quixotic endeavor.
I managed to test 4 different stack heights, plus multiple other changes in a 2 hours paired session on the Plasma 3 TT (PRO Missile Evo bars), and even more on the P5. It's actually really simple if you plan and you're prepared, and it boggles the mind why anyone spending the time and money aero testing wouldn't plan out how to make quick changes ahead of time.
The delta in CdA between the same frame in different sizes can be sizeable, and as I've said before what's fastest on one won't necessarily translate to another. Perhaps for those ecstatic about achieving <.250m^2 it won't make a big difference, but those who are serious about aero shouldn't, and hopefully won't, settle.