Slitherine

I'm currently playing that campaign. My understanding is that you can get 5 SE units. Is there a time frame in which you can get them like in the Grand Campaign? I was lucky and got a SE unit in the 1st two scenarios. Will I have to wait until a certain point later in this campaign to get a third one, fourth one etc.? This Campaign also has SE aircraft. Are any of them worth having over a tank unit?
Thanks for any help.

I think AK reaches a maximum of 8 SE units at the end - it's a while since i played so not 100% sure.
There are some capturable SE units available, which if I recall correctly can put you over the official SE unit count for a few scenarios. This doesn't matter much if you happily accept what you get given, but if you sell them off early either for prestige or because you only want SE tanks, then they might not get replaced for quite a long time.

SE aircraft can be useful from the extra attack and the extra ammo can be handy, but not all Tac Bombers came in SE versions so they are a bit limited and the fighters already have high ammo so an extra 1 doesn't help much.