I have a pair of EVM12L's in single cabs. Being a 200w speaker it gives me the option to use one or both of them depending on my needs. Closed back but the baffle of the cab has two 2" ports but I don't think they are necessary.
I'd say an EVM is perfect for a 1-12 [I've built and use two amps this way...one a combo and one piggyback].
Cover the back about 2/3. I first did the piggyback cabinet a bit too 'open' and was missing some low end until I made a new slightly larger back cover panel.