Combat Fleets average D5. Fast combat ships: Destroyers, Frigates, etc… range around 6-7, Slow ships: Dreadnauts, Monitors, Tankers, etc… 3-4. Corvettes and couriers go to 9. BCD’s (Burnhardt Compression Drives) aren’t so much super-high-tech as they are fuel/mass hogs which take too much space away from weapons, sensors, bombs, troops and other combat necessaries. They’d be very much limited to courier types.
One development this suggested to me was the idea of squadrons of combat “taxis”… basically BCD equipped hulls with giant fuel tanks. They would be fitted to warships to give them BCD capabilites in rear areas, but be detatched before the final move into battle.
-chris