I've triple hammocked under a standard army basha in the tropics!
The main things to consider are the logistics of getting into the upper hammock(s) and what the weather is doing.
You're likely to have less ability to shelter from winds (and/or rain) coming in from the sides. I'd have thought you'd be dandy in a 3x3 with 2 in all but pretty bad weather.
You could also:
- Grab a second cheap or light tarp to have two very close set-ups
- Both set up of a set of 3 or 4 trees that will let you set up side-by-side... Having a more flattened shape on your tarp to maximise the area underneath.
Both of these might be possible under a 3x3. It depends on the trees / supports. That's what I like about a hammock set up, as long as there's something to hang off you can create some really great camps!
Having said AAALLLL that, if it is someones first time out a cheap (or borrowed) set-up would probably be best? When I got the Mrs hammocking (on our Honeymoon - not the first night!
) I'd picked up a set-up on the cheap and gave her the Hennessey.