Zotting Superdreadnoughts....

I have also had this problem, the best thing that I have found is taking
about 4 strike cruisers as well as other ships. Several torpedo
destroyers
from book 2 are also good if yopu have the models, but the cruisers
usually
last longer, especially if the game is big enough to let you take a
medium
sized capital or two to stand up to the big boy.

Also, don't slow down too much - he's not that agile, and that big ship
will restrict the number of escorts he can field - keep your speed up,
take
a shot going in, go thru' his line, turn and then try to get in behind
him.
Of course any escorts that happen to get in the way with no capital ship
in
arc can also get fried. 

However it does seem that you get a result very much like the early
Honor
Harrington books - one radioactive dust cloud (ex-SDN) and one or two
gutted hulks with a few boxes left. Not the best for a campaign game
where
all parties will be an effective write off.

Happy shooting

Bruce S.R. Lee