Hi Coffex.
I own a 12" OTA and mount it on an EQ6. You can see a picture of it
in my bio.
It is heavy though, and it's a long tube. I don't use it for slewing all about the sky, I mainly do planetary imaging with it so it's just used for tracking once I put it on an object.
Paul Mayo (photonCollector) has similar, but his is on a G11. He does do marvellous deep sky imaging with it.
So, it can be done.