I ended up re-completing Alliance-15. For the Alliance from the 279(e) Alliance set. Luckily, I didn't instantly sell the M41 Bulldog that I used to complete it without honors the first time, and even squeezed out a 3 mark on it while finishing with honors. It was well worth buying that and the B-C 12 t back to complete both the 15's but I did find the B-C 12 t a little more difficult to get 1st classes on. With Coalition-4 out of the way I'm now the proud owner of a 279(e), thank you to everyone for all the helpful advice and tank recommendations you've provided.
For those still in the C