How about something along the lines of what the Soapbox derby has done in the past for gravity car racing (young teens in the US)?

Set up your formula format, offer scholarship prizes at local/regional/national/international levels (the higher the level, the greater the amount of the scholarship/savings bonds for educational use). By offering educational scholarships, the parent would have a “justification” to spend money on the project “it’s not frivolous waste of money…it for their education”, that coupled with the opportunity to make life long memories, teaching young teens how to work with tools, and share their love for sailing all accomplished at the same time.

The design can be tweaked to anything within the box rules, allowing for freedom of individual expression (just like the soap box derb, where people don’t complain about everyone not racing the exact same car).

The stock base plan you are working on could be offered for those who are not interested in “designing their own” but want to build, or used as a starting place to make modifications. Building "work shops" could be held on weekends to help children/parents who do not have wood working/fiberglass skills, given by volunteers who would like to share their boat building skills with the next generation

The rig could be offered for sale by the governing body just as the axles and wheels are for the cars. The youth get a local business to sponsor them by providing the funds to purchase the rig at cost from the governing body. By taking the expense of the rig out of the equation, the overall cost is substantially reduced, attracting more sponsors than if they had to absorb the cost of a whole boat.

Finding sponsors to fund the soap box cars is not a big problem.
A parent owned business, or employer is frequently the source. Many businesses would love to have their company name on the side of a cat, photos of them splashed in the sports section of the Sunday paper, the sponsors can pay for it out of there advertising budget..

A win for the child…he/she gets to learn how to build something with his/her hands, an opportunity to see it all come together from design to completion…experience not only sailing…but sailing on a boat they created. A win for the Dad/Mom who get to spend intimate time with their son or daughter, working on a project together and forming priceless memories while being able to pass on their love for sailing. A win for the local sponsors as they get to help a child develop character, and be a advertising partner in a unique opportunity that could ultimately expose his/her business to local/regional/national/global markets. A win for sailing as it has the potential to introduce a whole new generation to catamaran sailing.

A Win/Win/Win/Win situation...what more could you want?

This is just one answer of “How” it could be done.

Regards,
Bob