I’m with Oceans on this one, though I admit to limited experience.
I was working with a guy back in the early eighties who, through contact with his worldly shaping buddies discussing the what-are-we-shaping-this-year trends, started shaping chines on nearly all his stock and custom short boards.
It was shaped in from the tip of the nose all the way down to about the fins, or flyers as there were lots of them back then. Very normal rail profile and the chine was very small, almost non existent, softish edges sharpening up for the tail third.
In order to learn I shaped myself one, a 6’2" single, hard on both edges, nose to tail, and a fairly large chine. I wanted to feel what was going on. After half a dozen surfs I didn’t like it, so I sanded edges off, surfed it more and eventually filled the chine in. Glued on foam, shaped, glassed, etc, and got it to look like new again. It was transformed back into a normal board, surfed well, and had a long and happy life with one of the grommets who always scammed my old boards.
More recently though, mid 2004 actually, I rode a custom 6’ Glyder, a modern 3 fin fish shape by Shane Stedman. I know I’m not a three fin fan, but I won the board. The rails were chined nose to flyer, softish edges but very pinched, domish deck. Single concave to very slight vee, very square edges around the tail. Wider than I would normally ride with lots of tail kick.
I was a little sceptical at first, as I hadn’t surfed in a while, but the board just plain ripped. I’m 45, pretty fit and flexible, but I had probably only surfed a few dozen times in the last few years, and amazingly I felt like I was surfing like I was back in my mid twenties, and the board felt like I’d been riding it since then.
Whether it was the chines, the shapers experience, or my approach, I don’t really care. But I have no more bad words to say about chines, three fins in small waves, or the fact that age has nothing to do with it.
Have fun with your new board.