Legal question

Here's one I'd like to throw out to the group for an opinion.

As many of you probably know an airplane that may have been qualified for
the new Sport Pilot rating when manufactured will lose that qualification if
the gross weight has EVER been upped by STC, field approval ETC.

There are some aircraft that no longer qualify as an LSA aircraft due to
such a modification even though the plane is essentially identical to a
another aircraft that does qualify.

Examples Aeronca 7AC has been modified with the "No Bounce" landing gear and
has had the allowable gross weight increased. It is ineligible forever even
if the modification is removed.

An Ercoupe that had been changed from a C or C/D to a D model by limiting
the elevator travel and thus upping the allowable gross weight. It can be
made physically identical to an eligible airplane in 5 minutes, but is
forever ineligible.

I was approached and asked to "repair" an ineligible airplane by installing
a used airworthy fuselage, wings, elevator, engine, instruments, etc etc.
Essentially this would be taking an airplane that is not eligible as an LSA
and changing the serial number plate with one that was and annotating the
log as to the "repair".

The data plate, registration, airworthiness certificate and logs would come
from a pile of pieces that used to be a plane.

Being afraid of going to the pen and making little rocks out of big rocks I
refused. My refusal was countered with the P-40s and BF-109's that started
out as no more than a data plate. I was then challenged to run it by my
maintenance inspector.

I am loath to make a fool of myself and get on my FSDO's quack list so I
thought I'd bounce it off the group.

Would this be a case of forgery of official documentation---or a common
practice???

Cheers:

Chicken