On those K planes? Got similar my 15.6 Flatty. Its got a 8 inch pad, true flat, and 1 inch dropped chines and when they lift the hull and air under? Just gotta watch bow steer, and with twin fins under...? (basic never crank the wheel on plane as spit ya out!) They are called "Step an Trim"
Attachment 348188
The fins
Attachment 348189

