I’m doing more cross-countries now, working on my instrument training pre-reqs. There are a ton of non-towered airports around my home field, and I normally monitor their CTAF freqs while steering clear of their charted Class E transition space. I’ve heard other pilots make position calls when over-flying these fields at various altitudes. My question is, if I want to fly a direct route over a non-towered airport, is there a designated minimum altitude to do that without a position call? Not coming up with the answer from AIM. Thanks for any advice.