Nex 5 Audio Issues
Not hearing the video it seems like you're just clipping the mics. Essentially what you're trying to record is louder than what the mics can record. Being that most internal mics are omnidirectional covering the holes is only going to help marginally and while it'll reduce the maximum loudness but then you're going to 'filter' more sound through the body which is going to sound poor anyway. The only way to really find out if the external mic will work is to try it. As many concerts @ the stage is in excess of 120dB which will clip a lot of mics.