@doc_floyd Great question and what an amazing sounding adventure you are heading on!

You will be fine using permethrin on your new REI Gore-Tex rain shells. It is also worth considering pairing your permethrin with a picaridin product as that will give you more protection (particularly against biting flies) and will also not damage your new rain shells.

Have a great adventure!

John

At REI, we believe time outside is fundamental to a life well lived.