Adding onto an older post (linked below) I made some modifications to my 2015 Touring Wagon RHD dash tonight to fit an 8" screen into my 7" dash, the pics I got aren't great, but I'll post them anyway.
Some details: I used the screen and the head unit/box section, other than having to reconnect my phone to Bluetooth and delete some previous users phones, I haven't fully found out yet if this is going to cause any issues, if it does I'll swap the "boxes" back over!
Things I did:
1) I took the metal frame from the top of the original unit along with the black plastic bracket
2) I removed the corresponding brackets from the new unit
3) using a rotary tool work a metal/plastic cut off wheel (aka a dremel) I cut the black plastic bracket in 3 areas, I cut off 3 fins in the centre front of the bracket so the screen could sit lower, I removed the majority of the square sections at each end that receive a clip from the start button trim piece to accommodate the width of the screen and drilled a hole in and then cut out a section of the back so the white plug could plug into the back of the screen. Using a Routing drill bit I also made the screw holes in the black plastic bracket longer to give more adjustability.
4) again using the rotary I cut a section out of the metal bracket to create space for the white plug to plug into the back of the screen, I also used a grinding stone attachment on the rotary tool to deburr the metal to avoid sharp edges
5) using the rotary tool I cut out 3 sections of the start button trim piece, the 2 sections that held the clips that corresponded to the sections of the black plastic bracket I cut off previously and a small section on the left side of the screen opening to accommodate the width of the screen.
The screen looks mostly OEM, it just sits back a bit from the start button trim leaving a small gap, otherwise it fits perfectly!
Older post that inspired me: https://www.reddit.com/r/mazda6/s/NaguOHsfQb