Hey man i got the same amp. The last gig i played was for a school guitar class. We had a smaller stage, and it fit about 200 people in it. Some kid in class had a dad who supposedly knew a whole bunch of crap about setting up amps at the right angle came in to "help us set up". They worked and moved our stuff around while we did warm ups. In all honestly i didnt think it was that good, it sounded better then where it was but i didnt feel it all that much, maybe cause he was messing with my settings on my amp too telling my i didnt have enough mid, i gave him the finger and said its the sound i wanted lol. Anyway, my spider 2x12 was proped up with a chair on each side. All the amps were angled so the sound came together in the middle and blended into one. If you are worried about the open back, then i hear people stick a couple pillows in there to stop the sound from escaping, i havent personally tried this but who know. What i would do is take ur band and one of your other friends who knows music a little bit. Go the the gig spot, set up have him move around to different spots and tell you where it sounds good and where it doesnt, then move your gear around accordingly, also try with and without the pillows to see if u like it of not. also u guys doing cover songs or original? Anyway, gl with it let us know how it goes.