Ghost,
I'm in the process of training and so forth for the PRT as well. I always been able to run pretty well. Around 5 flat for my miles, but I am not saying that to gloat, instead to encourage to shoot for under 6 min. I had a great coach in HS for track, and his method to cut time under 6 is to go to a local track, warm up a bit and then start your mile run. On your second lap push your pace to about 75-80% of your max speed for 200 meters, then slow down to about 10% more of whatever your orginal pace was. Your heartrate will go up and you'll make it through your third lap a little bit faster than your first. Then on your 4th sack up and steadily push your pace faster till you get to about 80% or your max speed. At 150 meters try to run as fast as you can till you cross that line. I'm willing to bet you be able to increase your times dramatically, and then maybe even extend your workout for more endurance.
I hope this helps, it has work for me and my teammates very well.