Clemco, I don't think you are quite getting the point or say philosophy behind Paul's design of the LLF Mini. Click on the link to get it from the horse's mouth. It got buried in the forum and should be made a sticky next to his build thread.
www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=39791Edit:- This is the same link that Gizmo put in his post above.
You are mentioning a "maximum length and breadth" for an LLF Mini. The LLF Mini has a length and breadth which is it's maximum and minimum. I am not saying "Don't experiment."
What I am saying is that if you digress from the design parameters it will then be a "Clemco Mini".

With "Diablo" I stuck to Paul's plan except for a couple of very minor construction details which were easier for me to do than the way he had done them.
I am very pleased with the overall result and I am hard pushed to think of how it could be improved without designing a whole new yacht which Paul has done since then. The result is "Nappy Rush".
One little variation I would suggest is having two bolts holding the seat back support in it's socket. The sheeting pulls the support up when you pull it up hard. It is annoying to the pilot and will stretch the socket to a bellmouth shape eventually.
One of the beauties of the design is that the rear wheel base can be varied by drilling extra holes in the axle extension or even having different length sets of them.
I hope you are going to take plenty of photos and post them. I feel sure that you will do something different that we will all learn from. Cheers Cisco