Paul,  I just ran across these photos of a McClaren inspired replica
under construction.  Since I am (planning to)  scratch build a CH 701
including  a custom cowl, I  wonder if a similar radiator installation
could be implemented?   Probably the radiator would have to be angled
so that the air is exited downward.  One of the super light weight
Rotamax engines or an all aluminum single would allow the front of the
cowl to be extended forward if necessary to accommodate the rad
without causing c.g. concerns. Jerry

That is a good example of how not to do it.
Here is a Kucheman & Weber  type duct design.