I have a Power Train XL Harness that we originally bought for our Black Lab Service Dog(who passed away suddenly). We are now using it with our Mastiff Puppy (The replacement Service Dog). The Strap the goes underneath his chest, by the front legs, no longer fits; It's too small. I don't see a 2XL vest in your catalog. Do you have Strap Extenders? or a 2XL Harness? (He just turned 2; is still growing, and his final expected weight is going to be around 200 lbs.) Thanks in advance for your help!