Would help to have more info? HP of engines and RPM they are turning current props,as F2 Speedy mentioned. Prop shaft centerline to bottom of boat? Drive type? Gear ratio? Which 28? Pleasure set up, cabin gutted, etc.?

I would not worry about slip. I believe too many people hunt for great slip numbers with props; blades, labbing, geometry etc... and truly miss out on a good handling boat with proper ride in all conditions. Let's say you have props that are at 29" @ 24% slip 72mph, 44mph cruise, but you love all aspects about them. Carry bow, right amount of stern lift, great in rough water, plane good and you have nice speed. You then get a set of 26" @ 15.5% slip 71mph, 46mph cruise with an extra blade and you lose some driving ability is it worth having good slip numbers??? This had been my issue chasing slip #'s. I have 5 different style of props laying around collecting dust now. My Panther would porpoise with Hydromotives.
Just my $0.02

Agreed, I blew enough money on props just to have them compromised in another area. I found for my PP and Nordic a regular Bravo sharpened & balanced were consistently my best props. Now Brett a BBlades would have something different to say but after a certain point I just stopped and enjoyed what I had.

​​​​​​Diesels? In a 28? How does it float?

Where the OP? Darr?

Gigo

did not read any of the posts - only the heading.

check the bottom of the hull for a rocker --- possible ?

Too much stern weight ? any gained weight here ? water intrusion ?

Balanced hull ?

Prop a better one to carry the bow

trim tabs ?