From a post to Baen's Bar Honorverse dated March 17, 2009:

The Mesan Spider Drive

    …To the nameless Fly who sent me the e-mail pointing out (a) that the Mesan spider-drive ships mounting the attack on Manticore couldn't possibly tank enough reaction mass for the mission and (b) that the flare of their fusion drives would completely negate any stealth advantages of the spider drive itself, I will simply say that the spider drive ships do not use reaction drives. The scout ships do use reaction thrusters to propel themselves out of the freighter bays in which they were transported to Manticore, but we've seen Honorverse impeller drive ships using reaction thrusters to maneuver lots of times before. In short, this is not going to be a case of Honor's tactics at Cerberus, although some of the same "blind spots" which afflicted General Chernock's units at Cerberus do have parallels in Manticore's preparedness. (And, no, one of those blind spots is not a failure to look for visual cues from little things like massed fusion thrusters.)