No comment on balance, but be careful about the engine. Look at lml history.
As I recall Zehrback is in (or on his way to) the slammer for fraud.

-----Original Message-----
1.  Any thoughts about moving the potential weight of 2 adults farther aft
by 4 inches or so.  I'm considering installing the liquid cooled Zehrback
TIIV-650 which is about 90 lbs. heavier (wet) than the TSIO-550 and so other builders using  this engine are relocating their battery or installing A/C units as far aft as possible.