I've never learned to cast with the non-dominant hand up, and believe me I've tried. Most of the casts I use are single speys done Scandinavian style with the RL being done cack-handed. Even though when wading my cack-handed cast is actually better than the other way around, I did find it somewhat awkward in the canoe. The key thing for me was due to the use of the canoe it was rarely necessary to uncork prodigious casts. In fact, one of the things I had to constantly try to control was my urge to overcast simply because I could. Some of the spots on the Matapedia near town are a little wider, but most of the water of the Restigouche that I fished, which was the old Red Pine Mountain Lodge water, wasn't that wide at all. I would say that in most cases I could single spey out to about 80' on each side of the boat. If I had to cast farther I'd then overhead cast. What we do these days on the Muskegon in Michigan out of jetsleds and powerdrifters isn't really much different. The need to get the fly deeper means some tackle is different, like intermediate Skagit heads, and mending is quite different between steelhead fishing and Atlantics, but the casting is still pretty much the same.