Engine size does not necessarily equal comfort. My ZRX1200 needed help from Corbin in order to be bearable for more than a one hour ride, even though it seemed really comfortable in showroom first impressions.
On the other hand, I could ride my old '74 Honda CB550 all day long. A Honda 175 I owned was also reasonably comfortable. A '75 Kawasaki KZ400 became much more comfortable once I got rid of the stock "ape hangers" and put nearly straight low bars on it. My old 1968 BSA 250 Starfire was very comfortable on long rides, if only it had been reliable enough for long rides.
On the other hand, I could ride my old '74 Honda CB550 all day long. A Honda 175 I owned was also reasonably comfortable. A '75 Kawasaki KZ400 became much more comfortable once I got rid of the stock "ape hangers" and put nearly straight low bars on it. My old 1968 BSA 250 Starfire was very comfortable on long rides, if only it had been reliable enough for long rides.