Completely agree with Humble here. It is ok to fly with a squad only for FSO, but its better if you either join that squad in the MA aswell, or at least fly with them from time to time so everybody is on the same page. If you fly with a squad for FSO, it is always best to stick with that squad if its ok with them. Don't jump from squad to squad each week.
If you wish to get a squad to fly FSO with regularly, then you should be prepared to fly whatever side/type of plane that squad is assigned, and let them know if you cant be there for some reason. Registered squads have a number commitment to the event and can be penalized if they don't meet it or go over it. So make sure you are willing to stick with a squad and fly with them every frame that you can.
If you do this, you will build friendships and confidence from the members of that squad, and who knows, you may even decide to join them in the MA if they are an MA squad.
My .02
Gaidin