I've found that if you want to design a quad for "good" waves, you can get the best results by decreasing the cant and/or pulling in the tail template a touch. The theory is, you essentially double the vertical lift the fins create when you switch from a thruster to a quad, and when the wave size starts getting up to about head high, you don't need as much fin lift. So you can decrease the cant, or reduce the planing surface under your back foot. This will also help loosen up the feel... what Manisses mentioned.
As far as weight... it's really not a concern. We're really talking grams here. How much you ate before your session makes a bigger difference in weight than an extra empty box... or two. Many... many years ago, I was talking about mountain bikes and components and how crazy it was getting with guys trying to shave grams off their parts. The guy I was talking to said, "hopefully, the sack in my pocket weighs more than that."
true, but I was talking about hard bottom turns and going straight up to the lip on steep waves. I see some pros can manage that on quads, but others, not so much
i think that's a matter of dialing in fins, fin position, tail width, & spending the time getting accustomed to quads. very few pros (& only slightly more average joes) have really spent the time doing that. many will dabble w/ quads here & there...parko's statement was pretty telling...something about preferring quads in barrels (aka: going straight) but switching back to a thruster when the waves/judging requires turns.
we're so used to riding thrusters that when we hop on a design that we expect to perform like a thruster & it doesn't, we're very quick to discard it & say it doesn't work. you can push a quad like you can a thruster, you just have to tweak certain design aspects & aspects of technique...same as on a single fin or twin fin w/ a hp shape.
I have two quads, well one is a 5 box but still. One is a wide classic fish (4 boxes) the other a 6 foot diamond tail for chest and up waves with a thinner rail (5 boxes) I use the 375 for rear in both but as mentioned sometimes in smaller stuff it's to stiff. For that I took an old set of 375's and cut them down and sanded to shape about the size of a nubster (also made on of those for the 5 fin). Two reg front quads and the little trailers and you get the best of both worlds. Last month I actually rode the 5 fin with full size front, small sides and nubster when it was head high. Crazy loose but with drive and would tail slide like a mo foe!