I have had an AP 10" Mak, a TEC 180 refractor, a Tak 90 II, and an AT-72 all on an AP1100 at the same time.
No problem, though this configuration is only for viewing, not imaging.
This mount never ceases to amaze me with its capabilities and smooth performance.
This is not a permanent configuration in my observatory, but one that I mount occasionally.
I like the different width of field, visual views provided by each scope on a target. Adds context to the views, so to speak.
The two larger scopes are mounted on a dual saddle bar. Each of the smaller scopes is mounted on a bar on top of the bigger scope.