Ok, we have some data. All the estimates proved to be accurate and the tires fit with plenty of room to spare. See pics. The speedometer is off by ~4.6% (fully expected) so will need to adjust for it on the WH/Mi
I may do another test in a few weeks to get a better idea of what is happening but the short story is, we have little to no efficiency drops:
SOC: 253miles - Same as initial test
Weather: 35F, partly cloudy - colder than last time by 5-6 degrees
Driver: Fasted state, skipped breakfast, large cup of coffee in the car - same as prior
Car: Heat off, windows up, various types of music at half volume
Tires: New tires 265/40/21 and 285/40/21 were inflated to 40psi (personally I think these are the tires the car should have come with. plenty of rim protection and the stance looks more aggressive and slightly taller by about an inch.
Front clearance: went from 6" to almost 7"
Rear clearance: 5" to about 6" (sam as above, slight increase predicted by the taller diameter of the tire (~0.75")
PREVIOUS Trip Leg A: 8.2 miles (mostly on AP/FSD 50-55mph) - 264 wh/mi (terrain was nearly flat with small up/downs)
NEW TRIP: same trip details as above with efficiency of 272 wh/mi, but adjusting for Speedometer should be 272 / (1+.046) = 260 wh/mi
Trip Leg B: 7.9 miles (mostly on AP/FSD 50-55mph) - 251 wh/mi (terrain was nearly flat with small up/downs)
NEW TRIP: same trip details as above with efficiency of 263wh/mi, but adjusting for Speedometer should be 263 / (1+.046) = 251 wh/mi
So all in all, the car feels a little bit taller... a little softer on the bumps and overall looks a ton better. obviously longer term efficiency needs to be monitored but the initial feedback is very good.