Posted for Sky2high@aol.com:

 Cary,
 
 Cafe Problems:
 Generally, many people have chosen to represent CG calculations from the TE
 of the prop spinner.  This can lead to false results because of different
 propeller setups (wood/Hartzell/MT), long/short engine mount, angle of the
 extended nose gear, placement of rear wing spar (fuel), etc.  For example,
 You
 have placed the mains at P73.75 and the nose at P29.5 (P= from prop spinner
 TE).
 My measurements are P76.6 and P32.6, aproximately a 3 inch  difference.  It
 would be best to convert your measurements to FS (aft face  of fire wall)
 since the firewall/nose/wheel/wing relationships are equivalent  across
Lancair
 320/360 regardless of engine/prop/engine-mount combination.   In my airplane,
FS0 = Px - 36.25.
 
 Side notes:
 Remember that retraction of the nose wheel moves the CG back somewhere
 between 1/4 to 1/2 inch.
 
 Gross Weight calculations are related to what the wing can carry relative to
 stall loadings and max G's.  Also, it is important to consider what  forces
 the landing gear was designed to carry.
 
 You may be operating out of a 7000' low altitude airport, but some day  you
 will want to land somewhere else and, possibly, also take off from a higher
 altitude on a shorter runway.
 
 My airplane is a slow-built 320 equipped with: Hartzell CS  prop and 12 lb
 harmonic damper on the flywheel, short eng mount, small  tail, 9 gal header
 tank, 43 gal total and 1210 pounds empty.
 
 1.  Exceeding Gross Weight - I have flown (very carefully) at  approximately
 1960 pounds with the CG about 2/3rds back.   The autopilot could not hold a
 strictly level altitude (loss of pitch  stability) until 60 pounds of fuel
were
 burned off.  I would not  consider future flights at anything over 1900
pounds
 and would seriously  consider whether a flight over 1800 pounds is worth the
 added risk.  There  is no way to load these up without moving the CG back. I
 understand that  the 3 inch longer engine mount moves the CG forward about
1.5
 inches.
 
 2.  Do your own calculations for items moving forward. new CG = ((old  GWT
 moment) - ((change in arm)*(item wt)))/(old GWT)
 Using your example and a 22 pound battery moving forward 40 inches: new CG =
 (129960-(40*22))/1938 = 66.6 (old= 67.1) would move the CG forward .5  inch.
 
 3. My header tank carries 9 gallons at FS7.5.  Converting to your  example,
 7.5 + 36.25 + 3 = P46.75 and the moment would be 9 x 6 x 46.75 or  2524.
 
 4. Of course the bigger tail moves the CG back and the long engine mount was
 made available to help correct for that condition.  The long engine  mount is
 useful even if you don't have the bigger tail.  Let's say the  h-stab center
 of weight is about P240 and the engine center of weight is about  P20 so that
 each pound added to the tail requires 12 pounds added to the engine  to
 balance it without a change to the CG.
 
 5. Wingtip extensions - Hmmmm, more weight/lift on an already highly loaded
 wing spar.  I don't know nuttin about no stink'n extensions...
 
 Scott Krueger  AKA Grayhawk
 Sky2high@aol.com
 II-P N92EX IO320 Aurora, IL  (KARR)
 
 LML, where ideas collide and you  decide!