You guys are absolutely hilarious.
You can easily gain 7 pounds, or a half stone, in 2 months...you can gain 2-3 pounds a week if you train correctly. I'm not saying you are going to put on .5 stone of muscle but guaranteed it will be partly muscle, lots of water weight and some fat. It's called bulking. If you go to a BB gym you should know this already. BBers bulk for months on end, when their competition is coming up is when they start to cut. When you see them in the offseason they look like fat f**ks, when its competition time they are down to ~6% body fat but they are weak as shit because of the horrible calorie deficit. Go eat 5k+ calories a day, every day, and properly train...you must do squats and deadlifts, trials won't get your legs as strong as lifting would. and you will see serious weight gains if you don't just do upper body.
Most people here are all tiny and young, you couldn't maintain 6% body fat for too long a period...8-9 is fine, but 6 and under is competition level and your body wouldn't be happy with that for a long time. Calipers are finicky, the only true test of body fat percentages are water tanks.