I tried scratch building a 30 inch span canard for .049 power some years ago. The internet was full of hearsay and mumbo-jumbo, but no definitive CG calculators that I could find. The usual advice was to "build a chuck glider".
I found that in order for the canard to function smoothly and effectively, it needed to have a "stoopid lookin' amount" of foreplane area, no matter where I put the CG. With a "stylishly proportioned" foreplane [as in smaller] the model behaved like it had a toggle switch for pitch control.
It flew level just fine.
I ended up cutting the foreplanes off and flying it with elevons.