23 vs 20 Ride Characteristics

[Fr. Frank]

Sounds like you need to make two changes:
First, add stern lift trim adjustment via trim tabs or something like a Hydro-Shield skeg-mounted hydrofoil.
Second, adjust bow lift either by changing the drive trim angle underway, or change the propeller to one with bow-lifting geometry.

For stern-drives, the propeller diameter is more important than with outboards. You didn't say what the diameter, pitch, cupping and rake progression is for your propeller set, but if you know the part numbers for your props, you can contact PowerTech or Prop Gods and they'll offer good advice.
I do know that the closer your propeller blade tips are to the surface, the more bow-lift they produce. Other factors are important, too, but that's a good place to start. I would also put the drive into neutral trim where the anti-ventilation plate is perfectly parallel to the keel and measure the height difference. Prior to the wide acceptance of heavily cupped propellers, the drives (and engines) were mounted lower in the hull and on the transom. Giving that height difference to the techs at either of the places listed above may affect their advice on propping.