Roaming with two different Controllers (5520 and 9800)

I was wondering if anyone in the subreddit has deployed a mixed environment with the 9800 controllers.

​

Im currently planning on deploying the 9800 with 9100/3800s but we currently have 3500s and 2600s which I need to keep them on 8.5 with the 5520. I'm planning getting the controllers in the same mobility group and rf group (i'm taking a bet with that is going to work) but these access points are also in flexconnect so i need to see how they roam in different flexconnect groups. This is just with PSK currently so I'm not very worried on issues ill have with 802.1x roaming at the moment (that is a later problem but hopefully those 3500s and 2600s will be replaced by them)

​

This is just a temporary problem which i have couple solutions such as just finding the money so that we dont have a mix environment or moving access points so they dont do inter-controller roaming..

​

Edit: If i can't get rf grouping to work well then i need to do static configurations.. which will be a pain. Add to the question... if you deployed it in this mix environment how does RRM/Cleanair react

Im just trying to see if anyone has faced this challenge and found a solution. I'll be testing this in a lab in the next couple weeks so we'll see.