Avoiding noisy people is usually one of the toughest things. How many times have you downloaded a show and read through the included text file to see something like "thanks to the chatters in the crowd this is somewhat noisy" or "show was great except for the idiot in-front/behind me in the crowd"..
There really is no way to keep them quiet other than to re-position yourself. Sometimes (not often) you could mention to them you are trying to record the show and that you would be happy to offer them a copy if they try to keep it quite. 9 times out of 10 that will just get them more upset, and they will either run and find security or they will spot your mics and have a karaoke session with them..
If you are in assigned seating you may just be stuck and have to deal with it. Only way to eliminate the crowd noise is to think a head and get a group of people to go with you. When you purchase your tickets grab a few seats around each other and place yourself in the middle. You can not predict the crowd around you, nor can you spoil their fun at the show (even if their 'fun' consists of getting tanked and pissing in the crowd).
Otherwise, if you have a choice of where to sit. Go to the venue a head of time. See a couple shows get familiar with the location and find a few sweet spots that are in low traffic areas. You just have to use some common sense and get to know your surroundings. I am not sure what you are running in the line of mic's as you say custom batt box and custom mic's (im assuming some panasonic wm61a caps or something) either way maybe just get creative with your mic placement. Its a hobby just enjoy it try not to worry so much about the crowd. Worry more about your technique and creativity. Not every recording is going to turn out great. Just do not get frustrated if and when things do not go as planned. There are many other nights and many other shows to perfect your skills.
Take care,
Neil