CG
Hi Ollie,
If you look at the recomended CG of planes like the Zagi, you will find that it is in the range of 10% of MAC. For the flying wings that I have built, 10% worked out OK. Much further back than that and they are virtually unflyable. My recommendation to the gentleman that asked the question, is to start at 10% or so and then move back if he does not like the response. It is easier to fly a nose heavy plane than one that is tail heavy.
My 2 cents
Jerry