I haven’t performed the heatsink mod yet, I’m still looking for a metal shop that can cut the exact shape and dimensions of the heatspreader using copper 🙂 Found the designs at xda forums and figured that it should be better than a 20x20mm shim. It does get warm while charging, about 40 degrees celsius or so, while getting to high 60’s under stress tests. It idles at about 30-35 degrees though.