@ glad rag "How is the weight situation these days, esp for the "B" variant??"
Still underweight by 132lbs or so as of May 2015, measured on a Lot 7 aircraft. Whether this will still be the case when the additional structural mods are designed and installed is the undisclosed question, and there are two more years of SDD. But I'm positive that if the weight must grow beyond currently stated goals, it will be accepted, and operational parameters will be adjusted until a more powerful / efficient F135 variant (or replacement) is developed sometime way, way into the future (like after Block 4.3/5.)
F-35A is under by 372lbs.
F-35C is (projected) to be 286lbs under for a Lot 8 aircraft.