Greatlakestate

I am looking at the 12 1/2x3 1/2 large style billet vents offered by Eddie, Dana, etc. they are the ones with two round holes covered by slats. If any of you guys have these, I'd love to know the measurements of the holes themselves and their diameter and spacing on the vent. My 97 Chris Craft has the round deck vent holes just under the rear sun pad ledge..pretty much out of sight but they just have a simple plastic sleeve in them ( think cup holder with no bottom). I'd like to get something nicer and figured the billet vents might fit the bill. Thanks!