I've got a 1999 25 Daytona. With a 653 HP blower motor, 1.5 ratio bravo, on a 12" extension box. From my measurements propshaft is 1" below the very bottom running surface of the outer sponsons. Anyone done any trial on a similar boat. I've read that x dimensions is ideal but what about set back on a box, does that change things? So far best I've seen is 89 GPS with a labbed 30p bravo. Any insight to prop choice or drive height

I think you are about two inches too deep. I am at 7/8 inch above the lowest part of the bottom of the boat ( lowest point is forward about 10 inches ) and I don't have a box.

Yeah I took my measurement with a straight edge from the lowest running surface before the rear notch. Sounds like a shorty is just what I need. What prop are you running with that drive height

I am running a 28 Bravo 4 blade but I had to adjust for more negative trim to get the boat on plane. But once on plane ( very limited slip getting on plane ) I have a 11% slip. I just received a new BBlades labbed 30 BRAVO yesterday, I can't wait to try it out.
I shortened the trim rams 3/4 inch and did a little grinding for clearance to get the drive to tuck under the boat farther, It hops right up on plane now. The 28 got the boat right up on plane until I chopped 3/4 inch of the bell off of the back side.

I ran a 2" imco on it today. Ran 94.8 @5500 rpm with a box stock 30p bravo1 4 blade.

On mercury racings prop slip calculator that puts me at 9% slip, or I've heard some say the bravos are more like 1p down. So entered as a 29 would be 6%. Either seems pretty good. I would say lab work on the stock 30 would gain me a few more mph