Dear Y-G
"........I do not have intimate knowledge of current MRA4 performance, but knowing the capabilities of the MR2 and what has changed to make it an MRA4, I will still be very surprised to see it fly 6000 nm in one go."
Prepare to be surprised, as you appear to have very little understanding of "what has changed to make it an MRA4".
Comparing MRA4 to MR2 is like comparing a Series 1 E-Type to a Series 3. Both E-Type jags but completely different cars.