Hi Jim and welcome to the C-Brats. I see that you just joined today and yes there are several members that do tuna fishing from their 22' C-Dory. For one such individual......
Click on Search at the top header of this page and type in the word Tuna then go to page 4 of that screen and scroll down until you see a thread entitled "Rigging CD For Tuna". One of the CD owners (Mr. Fisherman) from Oregon does extensive Tuna fishing on his 22' C-Dory and has written about tuna fishing on that thread. If you click on his vessel's name Sea Lion, he has pictures of a few tuna that have landed on his vessel.
As you explore the search engine on this site, you will discover many other threads that discuss the topic.
Hope this is a help in search of the answers you are seeking.