There should be a baffel constructed to direct the air flow from the smile across the surface area of the engine head (typically this would be the finned area). The hole in the firewall would be between 2.75" to 3" diameter directly behind the engine head. Flexible hose of approximately 3" diam will extend between the firewall and the dump door.

It is expected that the flexible hose will be compressed somewhat by the cockpit floor between floor and the upper surface of the wing. This area can be bi-focated to assure adequate volume of air passing between firewall and dump door if required. Given the flexible hose it light weight and flexible enough it may not be necessary to bi-focate. This is of course dependant on the depth of cockpit kit you may or may not have. The Byron "cockpit tub" can be altered to provide adequate clearance between wing and cockpit bottom....the pathway of the flexible hose(s).