Thom,From what I see your going to be rite on the line of flying or failing 20cells weigh almost 3lbs. One standard rule of E-flight is that the power system is half the total weight of the plane or jet in your case.So 3lb for battery,now the rest of your system needs to be 1lb(motor/esc,receiver battery,servo's&receiver).If you can get the jet in at 3lb then you will be safer.Check the what the hacker motor max amp's are.According to what you posted your motor will be around 31amp.(voltsXamps=watts)Another thing I always do is a STATIC THRUST TEST! This is a simple way to check static thrust. I use a inexpencive fishing scale tie it on to the tail of my plane secure the other end to the ground (or something that wont move ) .With a fully charged pack and I also have my Astro Watt meter between esc and battery pack(I am also measuring total amp draw &watts) push the throttle stick to wide open and read the scale.Generaly you to pull AT LEAST 1/3 of the total plane /jets overall weight.For you I would want at least half or better.Say it comes out 8lb,you want 4lbs min.But 6lbs is what I'd look for.It may sound complicated but at least when you go to fly the jet you wont have to worry about a disaster.I hope I wasn't to long winded.Again good luck,stefanP