Dunno, In all tactical and squad based games I played (many... many.... MANY GAMES), I stick to 6 person in squad.
Tactical games with possibility to make more, I always ignored that and anyway made team with 6 persons. I don't know why, as well there's no significant difference, but 6 is great for me. So, no problem with current layout.
'bout xenonauts - I saw it - well, it's good. But why I want to help UFOAI project? Actually, I rly don't know. I love x-com, as well I can't see any big difference from all games (except shooter x-com... OMG, It's so wrong, but let's not speak bout that abomination), and I think it's great, as it's x-com core.
Still, there's something into UFOAI, something: mysterious. Xenonauts is nice, but UFOAI - Is great. Let's hope we'll make it DA BEST! XD