Lock the dome or not? (Canon 8-15mm and Ikelite 8'' dome)

Hello

I've got an Ikelite housing for my Canon 6D.

Unting now, when I've been using my Canon 8-15 F4L-lense, I've only used it at 15mm.

Then I could use the shade for the 8 inch dome, wich are were the locking mechanism to prevent the dome for rotating is mounted.

The locking mechanism is a small bracket, that's mounted on one of the set pins for the shade.

I just got my zoom-gear to be able to use the lense at 8mm, which is sirkular fisheye. To prevent the shade to be visible, I have to remove the shade from the dome.

The problem is: When I remove the shade, it's nothing to prevent the dome from rotating, and eventually fall off.

How do you guys handle this problem?

If your using a vacuum system, your port will be locked without a lock. the underpressure will keep it firmly in place.