I am running a 28 with 300 promax's, sporty lowers, bolted on the transom. I am a real world boater, I run with lots of fuel and 2 to 4 peeps and assorted boat gear.
I have always been made to believe that the 3 litres on a 28 makes it tail heavy. with that thought in mind, everything I have done is based off this belief. I am running oil bags to the outside, just behind the rear seat bulkhead.
I just moved the batteries forward of the front foot rest. I have dumped the heavy Skater seats for Sparko's. Prior to moving the oil bags approx 3' forward and moving the batts 8' forward I have seen (one time) 105mph with full tanks. (Bravo 32's with vent holes)

The problem: My props are showing more slip, my motors are seeing the rev limiters, and I've lost 5+ mph. The boat does not respond to up trim @ high speeds. Have I moved the center of gravity that far?

Sorry for all the wind, Thanx in advance, NP

first thing to check is are the motors still perfectly boxed, thats prob your 5mph plus i never had luck with those props

I hear ya. I run my boat the same way. Have 3" setbacks. Try some 4 blade dewald clevers. He has 30 thru 34's and some thru hub 5 blades.
Another friend on here tried some and picked up 4 mph. I can give you his number if you like. He ran them on a 28 with opti's.

I like the Mercury four blade lab finished Cleavers 14,5 x 32. My boat is all original and flys nicely even with the 300X's and a full load.

I have a spare set available that comes with a spare 28' Skater

Boxed? The boat ran 102 with 3/4 tanks and 4 peeps the week before I moved the oil bags and batts. thanx

I have heard good things about the Dewalds.

I know you're trying to help, but I'm not sure 2) 28's is the answer. l.o.l. I've got a set of 14.5x32 merc 4 blades, I'll give it a try. Maybe they will have less tail lift. Thanx

Are you spinning the props in or out? Do you know what the rake of props are?
I tried a set of 34" 3 blade Mercury cleavers on my boat and they were 3mph slower than my 34 4 blade Dewalds.

Props are spinning out, don't have a clue as to the rake angle.
are you running 2.5's or 3 litres? thanx NP

FYI I'm spinning in.