Moving propane tanks

[NVGun40]

Again, even if your generator is 135 pounds, you should be able to add that weight. Understanding that adding this to the tongue increases the TW on the hitch; regardless, if you are that close to tolerances....
However, Hohenwald48 mentions a good possible fix for your situation. The Stromberg-Carlson Tongue racks are good kit. Even if they cannot support a 135 pound generator, perhaps there is a way to shuffle somethings and place the battery(ies) on the rack and the generator down low.