For the record, one of my favorite techniques for dealing with special forces is, surprise, surprise, beachheads! Throw down 2 forcefields (or more), 2 mini-forts, some spider turrets, a few engies, and a moderate amount of escorting/defending units, and you got yourself something that will take on a very large number of special forces. I have been able to prune like 4000 special forces ships to 800 or so (numbers gotten from the debug info display) with only about a third of my defending units lost. That pruned down special forces enough for me to get past what would of otherwise been an annoying chokepoint the special forces loved to defend for some reason.