Why would the addition of the "trim rings" change the air flow?  I assume because the inlet area is reduced if only slightly and more likely that the smooth airflow is "tripped" by the sharp edges.  In my opinion, the "ram air" (quotes used deliberately) tube that is on most Continental-engined Lancairs is the worst I have ever seen.  The tubing is large enough - probably too large, but the sharp leading edge probably destroys any potential for pressure recovery.  And with it extending significantly into the cooling air inlet, those same sharp edges have to reduce cooling air flow.  What to do?  One of my favorites is to just put another air filter on the second inlet pipe and get rid of the mechanisms in the inlet system - they worry me anyway, as the small bits can come loose and go through the engine while the big pieces can come loose and block the air flow completely.  Use the higher pressure in the upper cooling plenum to give most of the pressure recovery that is possible - probably 75%.  What do you do about an alternate air source?  Maybe nothing, as half of the filter area is pointing backwards and won't be plugged with snow anyway.  Or just through away that pretty "filter" and put hardware cloth over the inlet.  My feelings about the effectiveness of K&N filters might be showing, I suppose.  At the very least just cut off the ram air tube and put a bell-shaped entrance on it.  Your idea of extending the inlet forward is good, but as Grayhawk said, to be most effective it has to be away from the hub.  This is because the round propeller sections near the hub are just obstructions to air flow.  I put my chin inlet (bottom-inlet Lycoming engine) close to the hub and it was a mistake, but I don't think it hurts a lot.  Take a look at some of the turbo 210's - they have a separate ram air inlet on the outboard edge of the cooling inlet and they have a rounded leading edge.  But for your installation how do you move it away?  I'm not sure, but I know what I would do - use two rectangular paper filters with a smooth transition from there to the throttle body.  Simple, works good, lasts a long time.  It would lose maybe 10% of what ram air could be obtained by heroic efforts, but a 10% loss in ram pressure probably represents 1% in power, or 0.3% in max speed.  And the extra air filter area would probably give 1% more power at takeoff and reduce the amount of dust by 90% compared to the K&N solution.  FWIW

Gary Casey

ES, Lycoming engine, paper filter from a turbo 402 Cessna.