Kinda silly to by used 7ah pulls when you can get new 8ah ones for under 25 bucks shipped on Ebay...
Depends on your personal preferences. I've got 8 to 12 of them, sometimes free, sometimes a couple bucks
each at a hamfest. I don't think I've paid $25 for all of them combined. If you want to experiment with them,
that's a good way to get started with a minimum investment, rather than putting out a chunk of money for
new ones and discovering that they really don't suite your operating style.
I would stick with 2 in parallel if you plan to work a lot. You will get more run time than using one battery at a time. It will also fade much slower as end comes never too.
Again, that depends on your personal operating preferences, rig, etc. If you're using a real current hog of a
radio, you might need two batteries, depending on how long you plan to operate. (In that case I'd use one
of my larger 33Ah batteries.) For a one-day outing, one of the 7Ah batteries is far more capacity than
I need, so I see no reason to carry two of them, especially for backpacking or other applications where
weight is important.
Parallel operation of batteries is not without problems: when they aren't identical or both at the same level
of charge, one battery can discharge the other. If you charge them that way, there is no guarantee that
the charge is equally distributed between them. My solution is to use (and charge) them individually. I do
have an adaptor so I can connect two of them in parallel if needed for higher current draw (or to run two
loads off the same battery, thanks to genderless PowerPoles). But if the battery is properly sized to the
application the difference in capacity is small, and the convenience of only using one battery at a time
and not worrying about whether they are in the same state of charge makes it worthwhile.