Engine doubling is intentionally disabled in SFB-OP, as Tholians or Andros with warp doubling are just too much, and not SFB accurate. It sucks for the Orion and Wyn but is the compromise I decided on.
Just remove the engine doubling line altogether and it will act as normal (engine doubling for cartel slots enabled), add the line and set it to zero to disable engine doubling for a more accurate facsimile of SFB.