Well, in hindsight, I probably would not have bought from REI. The 20% sale with free shipping was great, but then the three boxes of needed parts came in dribs and drabs. I got the rails in 2 or 3 days, then the landing pads a few days later, but the towers were doomed to be long in delivery. I got a note Thursday, pay $3.50 more to UPS and get upgraded delivery Friday, vs. Saturday for Surepost (exchange program with USPS). But, soon after I paid, they said, sorry wx delay, late Monday. I got them this afternoon, so ten days all told.
It was more the minor frustration because I got them now to buy a ladder that I need for two projects, and I watched the few nice days (including this morning) of November come and go while waiting for the towers.
It all went together okay. The Yakima video is much better than the instructions. One landing pad seems tight, but I imagine it will wear in, or I could file it a bit if needed (probably not). I do like the quality and look.
There is an "angle of attack" adjustment, but I think it's more to compensate for the slope of the roof front and rear, than any significant aerodynamic forces.
I will measure the total height later, probably not an issue, especially because the BOLT is relatively small to begin with.