Different base size

I want to maintain compatibility with other rules, would it cause many problems to have cavalry based 60mm wide compared to p&s units being 80mm wide. Not played Baroque yet but played allot of impetus a while ago and I don't think it would matter?

It shouldn't matter. My opponent & I have have discussed reducing cavalry to regular impetus sized bases and also doubling artillery bases to reduce the sniper effect.

in Baroque it is less important than in Impetus due to lack of Groups. This reduces the number of multiplee melee that is where some issue can occour (nothing that cannot be fixed with agreements between players)

I have rebased all my units to a standard Impetus 12cm frontage - I get more units from my figures, I can fight bigger battles on my 6' x 4' table and in my opinion it just looks better. As my only Baroque opponent has done the same with his armies there is no problem with compatability against other players! I keep the 9cm basic move and the game runs along nicely and ranges and moves still look realistic for the 28mm scale. I can get 1000pt armies on the table comfortably, something that couldn't be done with 18cm basing and I have no way of being able to extend my table.

Cheers