I've found "Fleet Swapping" in-gal highly effective. If you have alot of anti CR, and your mate(s) have alot of anti BA, and you have BA incs and they have CR incs, you send your fleet to defend a mate, they send their fleet(s) to defend you. It is especially effective if also combined with fake defence, ie you fake another anti CR fleet to another of your gal mates, thus potentially covering two incs with only half the ships
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The obvious counter if you think your target is likely to swap in-gal def or has a previous tendency to do so, is to send both a CR fleet and a BA fleet at him - that way if he defends his gal mate he leaves himself wide open.