"...the poor beast had improved wonderfully; it already seemed fatter and stronger, and had begun to show an affection for its new masters, especially for Sam."
So, my question is what is the dual form of cundu? It has a D so you should add a U at the end, but clearly it already ends in U. Is there such thing as irregular dual forms? Any explanation would be appreciated.
According to Parth Edhellen (in an import from Ardalambion), cundu is an archaic form of condo, the dual of which would be condu.
However, if you still wish to use cundu, the dual form of it would be cundut (according to dirk_math's wikibook on Neo-Quenya).