Engines, mostly what I've been saying and what I believe too. Once again, your post looks like you thought I was questioning the reason, utility or practicality of a feature of F-35. I was not. I was addressing a question about whether it had yet been trailed in the context of the QE class carrier. My remark about the marines was, in context, about their obvious choice to use VLs on the small ships; the point being that RVLs take space.
But thank you for the update and please don't think I fail to recognise the efforts of good people in the programme.
I shall attempt to be even more clear in my posts to avoid being misunderstood in future.