I did a Sea-To-Summit a few years ago. (
http://www.whitneyportalstore.com/forum/...=true#Post24502 )
I left Marina Del Rey and rode to Mojave on Day 1 (about 100 miles), Mojave to about Lone Pine Campground on Day 2 (about 125 miles) (had nothing left in the legs, so I walked up from there to the Portal) and then got up and climbed Whitney via the Main Trail on Day 3. I think it took me about 14 hours for what would normally be a 10 hour round trip.
Needless to say, my legs were fried.
I did this in October also. The days are short, so if you want to finish up before dark (I hate starting and ending a day in the dark.) I'd start up much earlier than 8:00am.
BTW, this is something that I've always wanted to do. Good Luck!