It's not just the weight of the camera that's a concern, but the torque that it will apply to the mounting ring on the lens (and in the camera, of course).

Torque is turning force, and it's calculated by multiplying force (weight, in this case) by distance from the center of rotation. So, if we guess that your camera is 4" deep from the mount to the back of the camera so that the center of mass is about 2" from the flange, and that the camera weighs 7 lbs, the torque at the mount would be around 14 in-lb. That's probably comparable to an EF 70-200 f/2.8 being mounted with no support: that lens weighs around 3 lbs and is about 8 in long, giving a torque of around 12 in-lb.

Even so, I'd want to support the camera for two reasons:

• Safety. You don't want to take chances with a lens that costs $11K.

• Stability. Putting a relatively heavy, unsupported object on the end of the lens will shift the center of mass of the whole system. Even if the mount itself is fine, expecting a rock solid connection to the equatorial mount through just one point might be asking too much of the lens' tripod foot. Connecting both camera and lens to a support system will help eliminate unwanted movement.

In the movie industry it's common to use a rail system as a chassis to assemble lens, body, and other camera components into a single unit. There's lots of good info online for DIY rail systems.

I just need to know what the acceptable limits are.

Reach out to Canon. If you're not already a Canon Professional Services member, you should be with a lens like that, and the CPS folks will be able to find out for certain whether you're pushing your luck with a 7 lb camera or if you're completely within bounds.

Reach out to the camera manufacturer. The thing you really care about is whether it's safe to mount the camera and filter wheel on your expensive lens -- you don't need to know about the actual limit so long as your use comes in under the limit. Considering that the manufacturer designed the camera to use an EF mount in the first place, they've probably done some research on the subject and may even have licensed the use of the EF connector from Canon, in which case they may have access to Canon's specifications for the hardware. At any rate, they should be able to tell you if it's safe to let the mount support the camera or if you need to provide additional support of some kind.