Thanks very much for all the supportive replies! It sounds like I should probably try a couple cold nights in the hammock in advance but it'll be great knowing I can bring extra stuff and others will have more equipment if needed.
The MAHHA sounds like fun, but I'm not sure if I'll be able to get there. In any case I look forward to joining a group hang sometime soon!
I've been considering picking up a plastic sheet and making a larger tarp and/or some beaks for my 8.5 x 8.5 tarp. I guess if I can find some Tyvek, that would be better?