What IS this CG formula you mentioned
"Using the formula from April 2012 "Flying Models" written by Greg Moore"
Please quote it here so that we can judge whether or not it is valid.
A photo or even drawing of the model would be nice too.
I have my own simple formula, but for flying wings I start with the CG at 15% of MAC
There are some online calculators that look reliable if you search on RCU. For example, look at the "sticky" above, especially post #'6 by
adam one
that leads to this site
http://rcplanes.000webhostapp.com/index5.htm read right to the bottom of the page and click one of the links there to get a useful calculator.
I generally treat a flying wing as a wing without a canard, rather than without a tail. I.e. I set stability to 10% as for a canard, rather than 15% as for a tailed aircraft.