Well, I'm still collecting data, but we've had our hot weather already. Unfortunately, I wasn't home when the local temp recording station hit 108.5 F (multi-decade record) to do a full evaluation. No...I was camping in 112 degree heat...not heat index either. But the wife was home and the AC kept up in stage 2. From what I've seen 4 tons is still overkill for this home, 3 tons might have done the trick although it would be close at 108.5. (3.5 tons would still have been the same frame size as 4 ton so nothing gained there.) When I was home it seemed to keep up in peak temps well over 100 F running in Stage 2 off and on for a few hours. Stage 2 would start to kick in late afternoon when the mercury crossed about 95 F. Balance point in summer is about 65-68 F...so 3 tons might just be adequate at 108.5 to hold my 79 F set point.
Before the hottest part of summer hit I cut back the blower to 400 cfm/ton from the 500 cfm/ton factory shipped default in 2nd stage. This improved dehumidification by a few percent, and it reduced the blower load (my vents are marginal at best at the higher flow.) Overall, it seems to run more energy efficiently and with greater comfort at this lower blower setting so I'm sticking with it.
The unit uses about 36% less electricity than the original when corrected for temp delta...even though the EER rating should be reduced somewhat in our several degree hotter weather compared to previous years. Might be better than that now that I've got it fine tuned. My back of the envelope SEER rating is around 16. It's been a pretty noticeable energy reduction even compared to last July which was hotter than normal but still over 4 F cooler than this July.