it's 12 hours... don't pack the kitchen sink. You don't need the blanket, just bring an extra layer to throw on if you need to. Don't need a puffy jacket either.
I had full uppper and lower thermal underwear layer (from marks work wearhouse) under my camo and that was almost perfect for the first nightfall.. if I had raingear. Another fleece layer would've been nice but at that point I was drenched. For those of you that don't remember the first nightfall was late october, started around 8-10C and dropped to about 2-5C overnight with 8 hours of rain. I was outside for all of it. If you have that layer for this time of year with a high of 20 this weekend, you're going to be begging to pull it off mid afternoon.
Add your transit time to and from the event plus the time it takes to load/unload/pack your shit back in to the vehicle etc.
See how many meals that time spans. Probably only 1-2 meals unless you have like a 4 hour transit to and from. You can do fine on cereal/supplement bars or 1-2 mres... if you like to torture yourself. In most cases you can eat before you hit the field and do with snacking or a light meal during the game on your feet and eat after you leave the field... it's only 12 hours lol.
Important thing is hydration more than how much food to bring... 4-6L total is probably more than enough even for the hottest of summer days. Cooler full of ice, carry 1-2L on you and put the rest in the cooler, refill when you need to. Although this time of year, ice is debatable. It's nice to have cold drinks during the day but leave some water out so it's not so cold for night, that way you can choose. No real reason to carry 4 kilos of water on you when you don't have to.
A change of clothes when you leave the field, either cause you'll stink, you're muddy/filthy or you're wet.
Bring ammo. Always bring more than you think you'll shoot. Cause sometimes you'll shoot so much and run yourself out and say 'fuck I wish I brought more ammo'. Leave it in the truck and haul only as much as you think you'll need.
The rest is fine. dust the boots before you put them on.. your feet as well. Depending on how much you sweat you probably don't need to dust again. I have a stick of bodyglide to help against blisters. I'm pretty sure it's just antiperspirant for your feet. I used that in conjunction with powder a few weeks ago when I was on my feet walking for 12 hours a day in japan, I had pretty good results. I've also used the glide in airsoft for the last year or so, it works fairly well. Depending on how much you sweat... or how absorbent your socks are... you'll still kind of sweat with this stuff on, you may need to reapply but last year at nightfall I was boots on for a total of probably 22 hours and I was ok with 1 application.
Roll of TP is deadly important. Even if the event has go huts, you never know if they are properly stocked or if they run out.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.