I agree the old style longboards versus give you a glide in light winds that you cant get with a formula. I used longboards 13 years ago , a Mistral Comp SST, then gave it way.
I rebought a prisitine but old f-2 lightning last spring. ( could not afford the 380)
Havent looked back.
the feelling of what i would call "the glide" in subplaning conditions is nice.
Going down even a very slight swell, you can sheet in, put you feet forward near the nose and reach speeds that you could not do on flat water ,
A weird but fun feeling of speed without planing.