From several homebuilt aircraft featured in recent magazines (HOMEBUILT, KITPLANES, EAA Sport Aviation) I'm seeing a frequent use of the "plenum" or pressure chamber used to force air onto the engine to increase airflow pressure for cooling. Doe anyone know if this is just a trend , for those wanting to invest in the fiberglass cap over the engine, or genuinely the accepted method of solving high engine temperatures. I dont see most F1's, or One Design high performance aerobatic aircraft using it, but see it used mostly on the RV's. I would prefer not to have the engine top hidden from my pre-flight inspection, as it would be with use of the plenum. Welcome any insight anyone can share on the use of the plenum.