I was testing a bit with different cores and layers of carbon under the core and one of my friends asked me what causes the core to print through to the carbon. And I honestly don't know the cause. This was Lantor Soric core in the example below.

I know and expect that it happens when using only a single layer... but the why is a mystery to me. Is it just that the core compresses more than the carbon under vacuum and moves the weave a little bit?
Pic for an example:

Great info as usual both of you! Thanks!

Good thought about using slightly thick material. This was just 3k but I will add that I did in fact chamfer the edges of the core (I used a razor blade to get about a 45 degree angle). I have some 12k at home that I'll try another test panel with to see if I can reduce the print through. I like the idea of using just carbon tape at the edges of the core, I know the last panel I made I used 2 layers of 3k and then the core material and there was no print through with that.

Thanks again!