okay,I Mounted an evm12l in my mark iv widebody... but never a III. My advice is that u should screw it right into the baffle. Also, make sure u use all the screws u can without damaging ur chassis(heavy speaker). I've been trying to get some pics of the new speaker in my mark iv. You have inspired me. They'll be up soon. One more thing, if u have never owned an evm before... They sound spectacular, very clean, clear, hi fi sounding speaker. When using crunch, it sounds crunchier, when using lead, it soars with a more distinctive cut. As for clean, u might need to spin ur tone nob a little more but the cleans are perfect. This speaker will duplicate the sound of ur amp almost perfectly. Just make sure its mounted right. Let us know what happens.