The "L" bracket Canon F4 fits the K10 and K20 almost is if it is meant for it.
The upright portion is on the user's left of the camera and does not block the door to the cable release. The base and sides of the body fit perfectly within the cradle of the bracket. The only downside is that the cradle of the bracket come very close to the AF/MF switch on the lens mount, but does not touch it. It retains its full range of motion. Access to the grip is not blocked.
I have the Manfrotto QR plates attached on the bottom and side of the bracket.
Please excuse the quality of the photos. I used my cell phone camera. My K20 was the subject of the photos!
p.s. This is the Canon F4 Camera holder. I have never seen an F3 holder or an F holder. The F2 holder has the bracket on the wrong side. The "Canon Camera Holder is for the old style RF cameras from the '40s and '50s. It won't work. The "Canon L" bracket is for the Canon 7. It also won't work.
p.p.s. The guys on the Canon film list will be mad at me!