I have some new vinyl windows I will be installing as part of a renovation. The existing walls are 2×4 with 1″ ridgid xps foam on the exterior then vinyl siding. No sheathing, no housewrap.  My new vinyl windows have a nailing flange and a vinyl siding channel. Typically on new construction of this type I would caulk the sheathing around the window opening then press the nailing flange into the caulking. I then install some type of butyl all weather tape over the nailing flange at the top and sides then lay the housewrap over the nailing flange at the top and side and tape it to the flange/previous layer of tape. I finish with a vinyl drip cap and vinyl siding.

In this case my plan is to caulk the nailing flange to the foam then tape the tops and side of the foam, maybe the bottom too.  I plan to try out 3m 8067 all weather tape. Does anyone have any other tapes or better suggestions? 

Unfortunately removing all of the siding to install house wrap is not a cost the homeowner is willing to tack on.\

Thanks