depends on the trainer, I've seen ones where the CG is almost 35% of the root cord, others were 18% - 25% ... well, wait a minute now ...
I'm told that the cg should be 1/3 the way back.
Were you just told this? Or is this what the manual calls for?
I had a Hobbico trainer and the cg on that was 2 1/2 inches back on a 10 inch wing cord ( 25% )... which, after the second tree it hit, I found out is exactly where the spar is. There is a trainer ... a tail dragger ... can't remember the name of it, but the guy was talking about the CG being 4 inches from the LE and had a 12.5 inch root cord. Well, just find out for sure, because there's a big difference between landing and crashing with style.