3: I don't see this. The engine can be mounted anywhere.  If you mount
the engine higher the prop will be higher and you will have just as much
trouble seeing over the cowl. There is no visibility advantage to
a internal spur gear box with the thrust line higher than the Mazda

The prop is higher not the engine.  This has two  advantages: 1.  There is
room above the engine for intake and accessories and 2. You gain ground
clearance for a longer prop.  The cowl does not have to curve or bump to
clear engine components.  It will be a  clean line from the fire wall to the
spinner backing plate.  This will impact visibility.   This arrangement
requires either cheek rads or a fuselage rad.  Either one can be made to
work with no more engineering than the under the engine placement, I think.
Once you accept this challenge, everything else is easier.  Until I see a
radiator installed  underneath the engine, that provides adequate cooling,
combined with  a good looking, slick cowl,  I remain sceptical.   I know it
can be done, but it will not be easy and it may not be better than the other
alternatives.       Jerry

OK Jerry here is a picture of the Marcotte PSRU equipped engine.
If you are concerned use a 14 inch diameter spinner rather than a 12 inch 
diameter spinner. The Mazda engine is only 14 inches high anyway.
That puts the e-shaft and thrust line down 7 inches from the top.

The Marcotte has less than a two inch offset. Also it is only ten inches from
engine to prop flange while the Ross and Tracy's are 14 inches from
engine to prop flange. If you use the stock length cowl the Marcotte aggravates
the weight and balance problem in most airplanes by moving the heavy engine 
forward  not to mention the ten to fifteen pound heavier weight PSRU right out 
near the front where it can do the most damage to the weight and balance.

Paul Lamar
 
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