Changed stem angle - what calibration needs to change?

[MultiRider]

I'm new to TT and still messing around with bike fit and aero position. My aero position worked well for the short TTs that I was doing (25-28 minutes), but was too aggressive (neck/shoulder/back/hip pain) for an upcoming 38km course (approx 1 hour). I swapped to a steeper stem angle to raise the front end (from 8 degrees to 16 degrees - Specialized stem with angeled shim) and I think it will be comfortable for an hour.

I'm using the RWS, so wind scaling won't change, right? All I need to do is reset the Tilt for the new stem?

Hmm -- as I type, I am realizing my CdA will change in the slightly higher position and my weighting on the bike will probably change, too. So I need to re-do all everything, correct? Coast downs as well as out-and-back?

My plan is to swap spacers to the top of the stem for short races and put them underneath for long races. So I'll probably need a "high" and a "low" profile? Will an inch difference make a significant difference in power readings? Less than 5%?

[coachboyd]

Yeah, even though your wind scaling shouldn't change, riding tilt could and your cda will. This will mean you will have a different aero and friction number. You possibly could get by with just doing the coastdowns and using the previous wind scaling and riding tilt, but if you are already doing coastdowns you might as well do the out and back ride.

[turbomentor]

I'm using the RWS, so wind scaling won't change, right? All I need to do is reset the Tilt for the new stem?

Hmm -- as I type, I am realizing my CdA will change in the slightly higher position and my weighting on the bike will probably change, too. So I need to re-do all everything, correct? Coast downs as well as out-and-back?

My plan is to swap spacers to the top of the stem for short races and put them underneath for long races. So I'll probably need a "high" and a "low" profile? Will an inch difference make a significant difference in power readings? Less than 5%?

From my experience: when I was NOT using the RWS on my TT bike, my wind scaling factor was something like 1.2. With the RWS, my WSF is around .88, so if it was up to me and I wanted the best possible profile for the best data, I'd just do a new set of coast downs and a new cal ride. 30 mins of effort on the front end will surely pay big dividends on the back end!