It might be but I don't see where it specifically says you can just add weight anywhere you want.
21 Authorized modifications (Strictly
limited to these items and their
stated guidelines)
Please note that, during a match, a shooter may
be required to demonstrate that their gun is in
compliance with Division rules by identifying a
specific rules clause or published interpretation,
which authorizes any disputed modification. If the
shooter cannot identify an authorizing rules clause
or published interpretation, the Range Master
shall rule that the modification is PROHIBITED for
Carry Optics use and shall move the shooter to
Open Division.