Just some notes from the accepted planes list on EAA site, don't know if it
follows the exact FAA guidelines yet but I think it may help with an answer.
"Aeronca 7EC's are normally certificated at either 1450 or 1500 lbs
gross weight, which disqualifies them for operation by sport pilots.
However, there are some 7EC's certificated at 1300 lbs gross weight. These
aircraft are eligible for operation by sport pilots."
From this it looks like the original certificate will be the "weight"
sticker. and it would probably take an act of Congress to change the
original certificate.

"Hatz Lyman C" wrote in message
...
SO who DO I ask.

You might start with the person who issued the Airworthiness Certificate.
I am
not sure if a change in Gross weight would require a new certificate.
Could be
that it is just too soon to tell.

Lyman