I found that 3.5g of rue made into a tea, then evapped down into a goo and encapsulated, was enough to have some pretty noticable effects on the mushroom experience for me. I had taken 2.5g of some average potency mushrooms.
I had some slight nausea with this, only for about 20-30mins though. Since I have IBS I was surprised I did not experience more nausea, but because of being use to having nausea I believe this helped me deal with it more. I was still able to walk around and function, no vomiting or anything.
Once the mushrooms kicked in though, it was definitely potentiated by the rue. It was maybe two times as intense as what it would normally have been, like you said. However, it never got really visionary because of having to deal with a fellow tripper having a crisis. Whenever something like this happens I sober up, usually people would just freak out but I believe my experience with such substances have helped me learn to control it and bring it down a few levels when needed. There was a lot more visuals then normal, but only in the aspect of things breathing/crawling everywhere. Never got to an OBE or anything super deep like I was expecting from this combo.
It is something to give a try though if no one has tried this combo yet. Just make sure you are ok with mushrooms on their own, and in large doses. I would say if you can handle eating an eighth to four grams, then this combo should be enjoyable.