Actually, mine has some of the 4-way stretch material. The black material around the wrist zippers is the stretch material.
IMO, for the heat of the valley and the Sierras....go with mesh. The rain liner makes an excellent wind liner in the colder temps and it "really really works"...road tested by
moi on the CFR adventure (rain 9 of the 13 days we were on the road).
It was a bit toasty riding home today in 100+ head and WITHOUT a cool vest. In the summer heat the cool vest works wonders. I doubt the 4-way stretch material will pass enough air to make summer riding tolerable.
Crash testing submitted for your approval.....no road rash after a 45 mph get off while riding the KLR. Uhm...other fragile body parts didn't fare so well with the sudden, head-first stop into the guard rail.