Grape completed a 30-miler not long ago. You've also got a good amount of experience with rucking, right? If you can both do the initial 12 miles in the allotted time then there's absolutely no reason why you both couldn't smash it. If you're fit enough then the rest is all psychological.
SC did that ruck with me.....
I could do the PT test, the 5 mile run and the 12 mile time ruck right now......not a problem. But even that gets tested due to weather, nerves, sleep, etc.
The rest is an absolute shitfest. In the last HTL, I think they did something like seven thousand lunges......this selection thing is way worse......they actively try to make you quit.