I use a 114mm Newtonian riding piggyback on the back of an 11″ RASA V1 mounted on a Paramount MEII. So, way within the mount weight limit. Seems to work very well (the 114mm is used as a autoguiding scope), but I could envisage trouble if it wasn’t being used in a roll off roof shed – as the slit of most domes would be too narrow.
British Astronomical Association
Supporting amateur astronomers since 1890