High Speed Smooth Fuel Efficient Hybrid Hull?

I have an 18.5' Bayliner Capris with a 3.0 Mercruiser setup that is a fuel sipper even at 35mph. When pushed she'll do 44mph. I love that little 3.0. The trouble is the boat lacks range and will beat its self to death on the bay in 2' short wavelength chop. I put air seats in it to smooth the ride and they work wonders but it's time for a new boat.
I don't pretend to know much about hull design but common sense says long and thin is smoother and faster. I'm wondering if I could build a 40' flat bottom hybrid displacement hull with a sharp nose to maintain the 35mph cruise, extend the range and smooth the ride? Needs room for four people and 100gal of fuel. I believe the only down side is that it may dig into longer swells. Of course it would use the same sipper 3.0 Mercruiser setup. Something like one of those 1940s' speed boats but a stretch job with the Dorado like nose?
I've found quite number of plans online but nothing like I'm envisioning. What a beauty she'd be. But, I thought to myself there must be a reason nobody is building boats 6x40 with old hull designs. Can anyone shed light on where I've gone off the rails? Man, this thing would even be trailerable here in Va.