[dmm]

1) Make sure your fleet orders are to "break formation" upon entering combat. (Assuming strategic combat.) Otherwise, he just has to toss your fleet leader backwards to disrupt the whole fleet.
2) Try using huge numbers of escorts with nothing but armor, set to "ram" strategy. Maybe combine with boarding party escorts. Set some ships to attack non-combat first, in the hope that he supplies his fleets by using supply ships rather than giving each ship its own quantum reactor.