Some VERY capable and VERY highly motivated folk have been kicking the folk who make things happen on MRA4, and the programme seems to be making headway (doesn't it?). There's no denying that there have been horrendous problems, but there's every reason to believe that P-8A's problems will be at least as severe, and several years later in being solved.
Too late to change horses now.
But in view of MM's support for MRA4, I wonder what he'd think of a dusted off R5, now?