Would it still be too heavy if I just do an expoxy coat and skip the glass? Just want to make sure that it's sealed.
dont worry about "too heavy"
or too big
or too much rocker.
......its just a piece of plywood.
it you dont speend too much time or money on it , you'll give yourself of luxury or trying a few different shapes and sizes for the low cost of a single sheet of plywood.
depending on your weight and wind the board may be too flexible.
however, flex is a good way to soften the ride and helps to 'dig your heels' in when you get over powered. Instant rocker
if you decide on stiffer...make it thicker, make it shorter, add some glass to the top and bottom.
(once its dry)
sun and water will help you 'morph' the shape ( sometimes good, sometimes bad)
fiberglass is effective in locking the shape you finially decide on as well as adding strength and stiffness.
as long as the board floats, it will plane and go up wind and even jump.
when you get to the point that you want more it will be an easy decision.
too heavy is never an issue until your repetoire of tricks is too good for plywood
sharp (including square) rails will release water.
round rails allow the water to cling to the edge.
the bottom still does most of the work, regardless of rail shape.
in a short time you'll be able to tell where you want one or the other.
in the meantime i doubt you can tell the difference
if you do figure it out on day 'one' you can easily fix your plywood board on day 'two'.
a 4 x 8 sheet of plywood will easily net 3-4 prototype boards that you can literally rip out in a couple of hours, total effort.
get to it, have fun and see for yourself what works.