speaking as a bigger rider (6'3", 185lbs), to keep up with folks who can climb, you're gonna need to put down in the high 200s or low 300s average power to make up for the weight. ~.5 mph difference is all weight, even just a few pounds.
I spent the ride spiking up the hills and then catching up to the draft then resting then repeating on the next hill until I am eventually dropped.
this is a clue to your fitness, and where to focus. (over/unders, sweet spot, threshold intervals)