Something I noticed just today: The TacOps Advanced Engine Master Table on p. 308 has a "Vehicle/Fighter" column for additional item slots taken up by the engine, complete with a (confusing) footnote trying to explain how to apply those slots to fighters. In addition to the types introduced in TacOps itself, the table also lists the stock Total Warfare engine types (sans internal combustion for some reason), with their extra slots taken up...
In every case, the number of extra slots is apparently the same for vehicles and fighters. So, while the TechManual states that none of the engines permitted for fighters there occupy extra critical spaces, Tactical Operations technically informs us that for example an IS XL engine does in fact take up two slots...and isn't even clear on where. ("[...] Fighter slots (if applicable) are located in the rear, with any extras divided evenly among the side wings." -- so, which of those two slots, if any, would be considered "extra", as obviously a single slot can't be evenly distributed between two locations and splitting both between the wings leaves nothing for the rear?)