Don't know anything about such things cycling in groups as I usually cycle alone, but I generally get passed and left behind when hiking up hills with BF. He finds it very hard work walking at my pace up hills, it's too slow for his legs. So he bounds ahead and then waits for me to catch up every now and again. I really don't mind. I know I'm slow. I would be of the same opinion when cycling in a group. Go at your pace, just stop and let people catch up occasionally. You're faster and stronger, nothing wrong with that. And if they ask about how they can get faster too, explain about the pedalling downhill.