I won't tie off to people I don't know. Complete strangers are a no-no as you can never tell what level of "give a crap" they have about thier boat. If they are friends, family, or friends of friends, or otherwise known entities, they're welcome to tie up. Part of the joy of boating for us is the social aspect, so we're usually pretty relaxed about that kind of thing.
Keep in mind, the below advice is from years of experience on relatively CALM inland lakes, and typically only within "no wake zones". We might get the random wake making it's way into the cove to us, but for the most part people moving around on the boats will create more movement than waves/wind/weather.
When rafting up one person becomes the "anchor" for the rest, and we start from there. We use the swim platforms as the "baseline" to adjust for length variations between boats. Prep ahead of time with all fenders out and lines ready. 2 fenders per boat per side. I carry 4, 2 for each side, and most others do as well. I also carry 4 dock lines for the same reason. As you motor in, go SLOW and make sure anyone in the water is aware of what is happening and floats away for a minute while you get in an settled. Tieing off to another "regular" hull is no big deal, just make sure the bumpers are at the right height to avoid boat-to-boat contact. Tieing off to a pontoon is a little more difficult, but again, just adjust the bumpers heigh from tie off to avoid boat-to-boat contact. Once tied up, then toss the anchor out, typically off the bow to help hold the group in place. DO NOT make the bumpers as tight as possible. If a wave/wake does come through then you are liable to have the boats off phase from each other and the back/forth can lead to contact that is unwanted. You want to have a little slack in there to allow for movement if the waves/wakes come through.
This is the exception, more than the rule for us, but it happens many times a year. I think there were about 15-20 boats in this raft up. Kids running everywhere, everyone having a good time. Sure I think I've gotten a scratch or two along the way. I think I dented my buddys pontoon rail once when departing. They're boats, not collectors items. We're there for the experiences, not to preserve an investment, and that attitude will get you many more good times and reduced stress levels than you might imagine.
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