So i finaly got an reply from the helpdesk where they said i could upgrade then for the index controller.
Then i asked since i am a backer that had switch from the 8K to the 5K plus if i could use the coupon to upgrade it to the index controller.
5 days later and still no response
My ticket number is #19622
Unless they have changed their position. This was answered search forum.
They said no to using downgrade credit on non pimax goods.
Just don’t confuse this with whether I agree with this or not. 
I tried as well but also asked if I could use the 10m cable pledge for the CK, which many confuse with the MAS (which should be a bundle IMHO) no response for one week.
Seems like that they have a lot of catching up to do. Nonetheless too long for a response, especially when a lot of those questions could have been answered in general at this forum.
Would have spared them lots of support work.
Agreed as many requested a simple Locked post FAQ on these upgrade trade credits.
I know I’m not alone,
But I am someone honest and clear
Why do you do that I do not understand
I am backer I have you preorder the 8kx
And that’s how I’m considered
From the support ticket system: I explained in detail how I didn’t want to upgrade, that I needed a label to return loaner 8K, I wanted a coupon for the 8k to 5k swap and for 3 10m cables I requested, I asked to keep the backer rewards, and that I wanted the base stations now and pimax sword sense eventually.
Finally got this response… Do you know our upgrade plan of backer?
I also emailed the NA support like a week before using the ticket system. I have yet to get a response there…