Gerry and all on the LML,
  The max gross weight increases have been "necessary" to keep up with
aircraft weight growth and a desire to keep the airplane a four seater with
the additional fuel added in the several variants.  I hear over and over the
landing gear can take these additional loads.  I wonder about the tires.  At
4000 lbs gross the mains are very close to their maximun weight bearing
capacity as stated on the sidewall.  And that is using the best available
new tires.  The nose tire has also to bear a huge load with either the
TSIO-550 or the Walter turbine hanging out there.
  The aircraft feels well loaded on take off at 3250 lbs.  Rotation and lift
off seem occur naturaly at something like 80 to 90 kts.  Landing touchdown
speed likewise is about 85 kts indicated in most normal situations tho that
can be reduced some with good piloting and above average skill.
  I set the max gross of IV-P 90Y at 3250 and soon upped that to 3500 lbs.
I think much skill should be developed before using higher weights.  The
aircraft on its gear is a bit skittish and directional control is a matter
of one's piloting skills being at the top of the game, so to speak.  Thank
goodness the rudder becomes very effictive at 40 kts.  It is a hot landing
airplane, no doubt about it, and requires a competent flyer.  There isn't a
lot of wing out there, especially those without winglets.
  A gross weight increase requires a log book entry, flight testing at the
new weight for an additional increment of time per the regs and stall
testing.  Many DAR's want to be notified of changes to aircraft they have
signed off.  Of course a new weight and balance must be made with most
forward and aft loading conditions calculated.
Walter Dodson