Bevo,
My apologies for not including the fuel bit in my previous reply. I can offer this, which was the situation in about 2006.
The 'VL bring back' weight for the F-35B included a mandated fuel margin, which was completely separate from the mandated internal weapon load of 3200 lb.
The fuel margin wasn't expressed as a weight, but was framed in terms of what the aircraft had to be capable of doing in terms of a missed landing. It had to have enough fuel left, after completing a full IMC approach, transition to the hover, and moving to above the landing spot, to be able to move back out and carry out another full IMC circuit, approach and VL to the deck.
To be clear, this was in addition to the 'bring back' weapons load. I'm sorry, but at this range, i don't know what the actual calculated figure was.
The 'bring back' requirement also included a number of assumptions, including (at least when I was on the programme) a degraded propulsion system and a 'weight penalty' to provide some margin for weight growth.
The people who put the F-35 requirements together had, correctly in my opinion, identified VL bring back as the performance parameter that had the biggest impact on the design of the STOVL aircraft and the propulsion system. That's why VL bring back was a Key Performance Parameter (KPP). When the programme experienced its severe weight problems in 2003, it was the predicted failure to meet the VL bring back KPP that first rang alarm bells.
Hope this helps, best regards as ever to all those smart people working the QE trials just now.
Engines