So what I tried...
at first I had the parity disk rebuilt onto the new 8tb
then swapped one of the data disks and let that rebuild from the parity
then stupidly tried to do the 2 remaining disks at once - preclear > rebuild
that lead to an error of incorrect disk config (something along those lines)
Then I follow some instructions here in the forum to use the New Config tool to fix that
It started to re-write my parity and lost all data except for 1 of the new 8tb disks
So ive started downloading stuff again and its spreading across the disks like the screenshots.
then tried that lead to just losing data, which is fine, I can download it again.
But now in redownloading stuff, its not spreading across the disks very evenly