if you still have the stock x-mounts that came with the motors then you can use the motor mounts Yuri (Irisaerial) cut for me when I made an X8 from my flat 8. They're cut from 1/4" sintra which is PVC sheet plastic. They've worked fine for me and others and I'm still flying an XY8 with them for over a year now. I'll check to see what diameter arms they're cut for.
Where do you live?