I have a problem with my carriers colliding with their escorts in the patrol box. Is there anyway this can be reduced/prevented?

I haven't seen collisions in a long time, so any mod you're using could be responsible.

 

You can try making the patrol box bigger so the ships will change course less often. And make sure you have no slow ships in the group - if they are in front, the others may over take them.

 

It's a shame the game doesn't make ships avoid each other and land. (Not that the planes are much good at avoiding land either).

What version of IL-2 are you using?

In one of the latest versions, damaging a ships slows it down and causes collisions.