There are some contests that are well attended year after year (sold
out) such as "The Seniors," and a few regionals. It may be possible to
have a similar format with a "Class" or "Classes" mixed in and
appropriate trophies awarded.

Regional / National contest with Sports, Standard Class and/or 15 M
would fit fine. Even the 18M and Open Class could participate with
seperate, but similar tasking.

Some contests are too popular to allow such a mix. Such as The
Seniors, and Perry

Tom Knauff