I,m not sure what you mean by cowling so I presume you mean to steam bend the cockpit coaming, not just the rim on the coaming. This should work fine as long as you can manage to match it to the shape of the hole in your deck. I thought about this a little and decided that I would have to make a replica of the deck as a form. Could take a piece of plywood, kerf the backside and fasten them to stations which repeat the deck stations at the cockpit, you only need them to be a few inches deep. I couldn't think of a way to form on the deck itself without deforming or possible damaging the deck. The other alternative is to make it a few inches wide and trim it later to fit the shape of the deck. Either way is probably a lot more work than either bending strips of plywood into the hole and trimming or using "little soldiers" strips vertically. My thought was that I could avoid glassing the coaming and rim if I did a nice job steam bending hardwood.