Thanks so much for your replies.
The Flexwrap by Tyvek is butyl rubber and not normally compatible w/asphalt but I have heard that the #15 doesn't have enough to worry about. Down here we are required to cover window flanges, sides and top with sticky tape by code and I first put the flexwrap on the window sill and 6" up both sides and then mold it down past the sill onto the wall on the bottom, then install the window, then cover side and top flanges with sticky tape and then lap the felt over the top.
Under the double layer of felt is osb 'windstorm'.
I'm glad to hear from you both because I've read the things you've written in different posts and really respect your opinions. I actually didn't really worry much about any of this until I started reading alot here and studying about drainage planes on walls. Now that I want to do things the very best way, I'm almost having to tie the framer up and force him to do it. He wants to use Typar or whatever tyvek makes for stucco and I do not. I want the 2 layers of felt. I do like the idea of 30 in back and 15 on the top.
Since I'm required to use the tape over flanges and want to have the felt under the flanges - if it doesn't stick well, do you think it would be all right to cap nail it on? And then put the 2nd layer of felt over that?