LFS4 prop reviews

[LPowers]

Currently have a 3x16x20 prop on a 07 df175. Hitting 6150 RPM's at 45 mph. Thinking of going to a 4 blade for a few reasons. Motor is at its lowest mounting hole and my plate is still below water about an inch. Boat seems pretty stern heavy with the rear livewell full and full fishing loadout and 3 people. About how much stern lift can I expect? Also how much will my RPM drop with the extra blade? Maybe the 4x16x19 would be best fit?
Thank you