GYA is your standard run of the mill regional sailing authority...
CBYRA is my run of the mill regional sailing authority.

15 years ago we faced the same issue.... The solution, the beachcat sailors formed a handicap racing class and joined the YRA. We were separate from the then cruising multihull class CMA class. (turns out the absence of a head was the only requirement the beachcats could not find a work around for in racing under the CMA class rules)

Still... each OA running an event makes a decision on what classes they will offer a start to... Just because you are a member of the YRA does not let you force your way into an event.
Clearly there is a difference between the two types of vessels and common sense argues that the YRA and the OA manage each class differently.

Simple solution... organize the beach cats... go to the meeting and work it out.