Don, I don't have vented lowers on my '04 SEEG and the SERG is still a noticeably warmer ride.
Guess it's the combination of the design of the lowers and the 100% fixed upper fairing on the Road Glide (no removeable/adjustable wings). Any sort of vent in the lowers would be helpful.
I was surprised when it was so immediately noticable on a mid 70 degree day. Enough so that I know a truly warm day would be an issue. Wasn't riding on the highway. But in town mid 70s made for a toasty leg even while moving.
The red bike is the only bike I've ever owned with lowers other than leather or vinyl things that could snap on and off in a minute or two. So it was my only comparative experience. The vents on it work well enough I never take the lowers off. Just don't need to.
This Road Glide will almost certainly see them seasonally removed though. At least until I come up with some alternative cores and get them painted. Have no idea how much of the difference is the much larger and fixed upper or the lack of vents in the lowers. But any extra venting will have to help. Guess we'll have to experiment a little and see what helps.