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

Offset shafts can be  used to advantage.  My drive (when it is finished )
will have 5.1" offset.  I used this to lower the engine 3" and still gain 2
inches ground clearance.  Ground clearance is an issue with higher hp
Tailwinds that need to swing longer props. The five inch offset totally
eliminates cowl clearance issues on top of the engine.

I agree, both the weight and length of the Marcotte are disadvantages.  We
are hoping to come in around 40 lbs with the chain drive but won't know
until it is put on a scale.

Jerry

 
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