A couple years ago I had a short discussion with a well-known multihull designer about the advantages and disadvantages of adding amas to canoes and kayaks. During our discussion he told me that sailing canoe aficionado Hugh Horton seemed to be generally against it.
Hugh is known for designing canoes such as the Bufflehead. See here for another article about Bufflehead.
The following link attaches to an article written by Hugh that details some downsides of adding amas to paddling/sailing canoes (and kayaks). It’s a worthy read and based on his experiences on the water, along with some friends. Here is the link: Tales of Multi-hullers: Wouldn’t It Be Great?