nonstop

Last year was running my boat at the end of the season. (1988 24 Scarab Concept /single step with pad). The 27 was a pain to get on plane, boat would twist, give to much throttle and it would break loose until you got rolling then it was good. Mid to upper 70's all day long. Decided to switch to a better cruising prop. Called Hydromotive, spoke to Todd, Told him my set up and said the 26 px5 would do the trick. Great prop. No more twisting or breaking loose. Right before I made the switch to the hydro I noticed the 27 would let go at 5000 like hitting a light switch. Was not sure what was going on and then realized the cone had come off. That was at the end of last season, mid November. Called Todd at Hydromotive today and told him what I found. He is telling me there is no way not having a nose cone is the problem. I said it was breaking loose at 5000, not 4600 or 4800 but 5000 every time. I'm worried with a cone the PX5 will grab to much water now and slow me down. He said that adding a cone might drop me down 50 rpm but it would not slow the boat down. I'm thinking it will because the prop will be getting more water and if I'm at 5200 wot now I thinking it will go down more then 50 rpm.
I wanted to put a cone back on to be more efficient but will it even matter one way or another?