Underline and exclamation point on that amen. There is a certain expectation in being part of a "group" otherwise what's the point. My advice is to get it out in the open before the trip. Otherwise, just make a loose commitment to meet at some spot on the map. Just drive separately. As long as everyone knows what to expect (and is reliable and proficient in the back country) it can work out pretty well. I'm generally pretty mellow; not really into telling people what to do. But make me go looking for you for an hour or two, and then I find you lounging at a creek (and not dying) when you are supposed to be somewhere else; you are going to meet pop-a-vein.

My worst experience was with scuba. We are doing a beach dive in the tropics and Howard comes up to me and asks do I want to partner with him. He is part of the marine group and these guys dive basically alone all the time. I did not really register this and said sure. We hop in the water and in two minutes he is GONE. I didn't see him again till I got out of the water. Lucky this was a shallow dive. Still had a good dive but......never again with Howard as a "partner".

Not that you need this advice...I just been gone for a while and felt like commenting on something!