My '91 42 Fountain has -2 shorties on it but doesn't have the IMCO cav plate extensions on it. It gets on plane with no problems whatsoever but it does take a lot of trim to carry the bow. Running 24p Bravos. Would I benefit from these?

the cav plates only help if you are blowing out getting on plane, they won't do anything to give the props more bite when you are running at speed

That's what I thought. This thing gets on plane easier than just about any boat I have ever owned.

As stated the anti-ventilation plates help when your props are ventilating while trying to plane. The shorties won't carry the bow because the shorter drives have less leverage.

If you are running stock Merc props cut off the defuser ring on the prop with the higher X the defuser lifts the back of the boat causing more lift at the transom making it harder to trim out .