Hmmm.... To the best of my knowledge, a Northwest Forest Pass is required for any rig that will be parked overnight in the Naches/Manastash trail network, including campgrounds. Unless you know something I don't John, I'll call Mikki Douglass over at the Cle Elum station to confirm. We used to go round and round with this issue, finally settled on this interpretation:
Day Use: You don't need a pass to drive out, wheel for the day, and camp outside the trail system/official campgrounds.
Overnight use: You need a pass to park a vehicle(s) overnight on the trail system/ official campgrounds.
Tow rig: Only 1 (one) pass is required per user. Leave it in your tow rig that stays in camp, as the rangers can ticket any rig parked in an official campground without a NW Forest Pass.
So maybe what John is getting at is that Long Meadow (which I believe is the common name of the area we're camping at) is not an official campground, thus you are not subject to NW Forest Pass rules. I honestly don't know, but I'll give my ranger contact a call in a few hours and see what she thinks.