A 6120m is a grand tractor but it will be on its limit with the cooling pack being crammed in .Definitely not one to chip or remap...The dealers turn a blind eye around here, as it doesn’t show up apparently. Just don’t take the p**s but another 20hp will never stress anything on an owner driven tractor. I wouldn’t worry about weight as it’s easy added, we filled the back tyres with water on our Fendt as it was so light on the backend but jd are heavier so I don’t think you will have any bother.