Jim

Flutter analysis (as done by Martin), uses finite element analysis.  The
stiffness of the materials, support and the natural harmonics of the system
are calculated.  And aerodynamics will also affect it.  With all those
variables, if you're changing something, it would probably be a good idea to
have ity analysed.  Or, he has a really interesting two day course that you
could take and you get to keep the FE software.

And you should also consider that the extra fuel outboard will increase the
gyradius (mass locaed away from the CG) and make the plane more resistant to
recovery from a spin plus, kerosene is about 16% more dense than gasoline,
(6.12 lbs/ga vs. 7.13) so while the quantity may be the same, the weight is
different.

Dan Newland