I wouldn't want to cover up *any* vent either. When I put my registration # on my Phantom, I used a Brother label maker. The labels aren't very big and you can control the print size to three different sizes. I put the resulting label on that little "ledge" just above the battery.
At the moment, it looks like a court case has thrown out the FAA registration requirement. Because sometimes the law moves so slowly, I've left my registration number on my phantom - and my Chroma and my QX3 and my ....
Hopefully some of this nonsense will get ironed out soon. I wonder if the FAA will give me my money back? Oh that's right - they already did LOL.
Art - N4PJ
Leesburg, FL