To be honest - not sure about how I handle altitude... Rode both sides of the Stelvio then Mortirolo Gavia loop the next day just last September after flying in from sea level and minimal hill repeats prior and felt fine there. But the Stelvio is only 2757m and the Gavia even lower at 2621m...
Preliminary checks have the minivan hire over double the cost if a one way hire from Denver to LA, so now more likely to drive from LA. Therefore I could drive out via Tuscon to ride Mt Lemmon and Mt Graham first before hitting the Colorado climbs later that first week? Don't want to wait too long after landing to hit the CO or Sierra climbs though in case the snows come early.
Thinking about looking at hiring something like a Dodge Caravan / Chrysler Voyager were the seats fold into the floor, so I can sleep in that some nights to keep costs down.
Actual dates are still very flexible, unfortunately looked at my leave and I have only just over three weeks available by late August. So I'll need to fit as much into a short visit!

