Crude drawing of how you laid out your measurements!!
Thanks

You definitely dont want too much weight on the front wheel

Just be mindful that the International Mini5.6 is still a class in its infancy and there is some basic design principles but they would not enough to be locked in as exact measurements, and many of those have just evolved.
I believe the original LLMini was built to the same wheel base as a blokart as a one on one comparison.
With the Mini5.6 class there is no sail size restriction, just by changing a sail will alter the for / aft balance...... This is one of the greatest things of the class, there are VERY few design and building restrictions.

And remember the 5.6m rope rule is a MAXIMUM measurement, yachts can be built smaller than that.

Im not sure what the measurement is without some sort of diagram, butsince you are sailing on clay,you will be able to move the weight and the mast back further than on sand,due to the better grip on clay,OR run a bigger rig.
OR you can run a more manta like rig with greater rake and mast moved forward. again because of the great traction that clay provides. on clay I move my weight back till the front wheel just grips,and bend my knees to turn.
BUT the same set up on sand or gravelwill make for very squirrely sailing. the best gravel/sand yacht ive had was "nappy rush(photo please cisco) But in racing I frequently lost control. by moving the mast baseforward only50mm I brought the beast undercontrol,but lost alot of the racing edgyness that it needed to be a great racing yacht