every company gives a recommended port area, or people like to use about around 12-15 square inches of port per cubic foot. ive got a rl-p 15 and am drafting a new box to fit under my hatch cover for better security reasons. my current box is 4 cubes after disp. at 30hz w/ 55.5 square inches of port.(in love) the one im drafting is will be 3.5 after disp. at 32.5 w/ 67.5 square inches of port. i dont know when i plan on building the new one, maybe when i have the cash flow and a job lol

so how do you know you

No such thing, as long as it's tuned correctly.

I would say it's "too big" when its so long it can no longer fit in your application/car.

No such thing, as long as it's tuned correctly.

I would say it's "too big" when its so long it can no longer fit in your application/car.

the only thing i could think of would be reduced power handling because of a bigger box but not sure. not really an issue here.

There is a rule of thumb in terms of if you were competing.

Never make the port larger than the total surface area of all subs combined.

In your case, don't make it any larger than 175sqin.

I do know port area affects output potential. Too small can limit output but too much can also do the same thing i'm sure. Just like installing a super large exhaust pipe on a stock car. You've eliminated a lot of back pressure that it once used.

There is no for sure method of knowing too much is too much without testing but for your scenario, there is no way that would be too large.