The plans give the shape and location - see attached. The plans location won't fit the Cozy Girrrl extended strakes, and I adjusted to just below the strake and below the trailing edge of the canard.
An alternative to the plans dimensions is using the Van's NACA scoops, and I bought a set. (It comes with NACA scoop, adapter and hose - can I use the extra parts for cabin heat?) That scoop ends in a 2.0 inch outlet which needs to map to a 1.5” mating collar on my eyeball vents. I made some custoom scoops, then some large-ish adapters, fussed with a high performance RTV, then went simple - a 2" plug goes in the CAT hose, with a 1.5" cutout that fits the vent. The plugs are 2 layers of BID each side of 1/2" blue foam, with nested circular cuts made with my hole saw kit. The ends are secured with standard hose clamps.
(This is another instance of where kit builders save a heck of a lot of time - they just install the supplied parts. Yes, I could have followed the plans, but then I wouldn't be building with enlarged strakes, et al.)