For me, it's 5 trips.
I start by gutting and skinning so the meat starts to cool. If I have a pocket saw with me, I also trim the legs. Otherwise I fetch the saw when I get back to the truck with the first load. Here's how it goes:
1. First trip, I take the head and all my gear. I fetch my pack and bags.
2. Rear quarter
3. Rear quarter (w/proof of sex)
4. Both front shoulders plus brisket
5. Backstraps, neck meat, rib meat, and all other loose meat
