I'm almost certain you cannot use Cataracts or std size Sawyers on those pins. Look at the diameter of the aluminum oars on that boat- the knobs on top screw down against the oar shaft to secure it....those pins will not reach thru the larger diameter whitewater oars. Cataract and Sawyer make a smaller diameter oar- Scadden sells a version. I wouldn't use those with a knob and pin oar lock system either.
The recommendation for a frame is your best bet- it is the only way you're going to get the power you will need for even 2 people- let alone 3. Jacks Plastic sells a small fishing raft with a small frame- take a look at that for an idea of what would work. It would need beefing up- but it gives you an idea
Sent from my SM-N900V using Mountain Buzz mobile app