Jeff,

When checking for wasted inlet area, consider checking the necessity of having the Mazda oil cooler.  From a previous photo, it appears that the oil flows from the pump to the Fluidyne cooler and then through the Mazda cooler.  The Fluidyne oil cooler may be of sufficient capacity to handle the oil cooling by itself.  I replaced the stock RX7 cooler with a Fluidyne DB 30618 cooler of similar dimensions and the improvement in oil cooling was dramatic.    The three RX7 coolers that I tested all behaved identically in that at RPM above 2600, the pressure at the inlet to the cooler was about 150 psi and independent of RPM.  It didn't matter whether the oil temperature was 160 or 230 degrees.  This means that at an RPM of 5200, half of the oil is being dumped directly back into the oil pan and not going through the cooler.  With the Fluidyne cooler, all of the oil is passing through it, the back pressure is only a few psi, the oil temperature at its outlet is less than 200 degrees in climb with an OAT of 90 degrees, and less than 1" H2O pressure across its core is sufficient to keep the oil temperature at the cooler outlet less than 190 in cruise.

It is possible that the Mazda oil cooler in your system is acting purely as a constriction to the oil flow and its internal thermostat isn't doing much.  The Fluidyne cooler may be operating at 150 psi or more most of the time and is doing nearly all of the oil heat dissipation.

If you haven't done this already, it may be very instructive to check the oil pressure and temperature between your Fluidyne and Mazda oil coolers.