The tri's did well pedaling from the stern. The O30 team Hot Mess managed with paddles and 4 guys. Team Kelp is using oars from the cockpit. The best power will be from the transom so depends on your time available. A sliding seat in the cockpit is a bit of a challenge too, but teams have used old rowing machine setups on thwarts and such. It is nice to have the paddles as well, to use different muscles for a while or supplement the rower's output. The most impressive setup was on the 40 foot carbon mono, with a multiple pedal set up and crew on trapeze, using the apparent wind, for 6 knots of boat speed.
2016 the wind was so strong getting out of Port Townsend that it was a real struggle for some, with boats pushed on the seawall. The Thunderbird team struggled with the freeboard rowing there boat.
A folding platform on the transom is my suggestion, along with paddles to help steer. I have seen wood ones listed on CL from mobos, just add hinges.
I have some used oars for sale.They are 12 feet, with a cupped assymetrical blade and a wood handle and are light. I have a set for myself, my buddy and have a couple sets left to sell. I am selling them for 50 a piece to r2ak teams. They are in good shape. I also have an older aluminum rowing frame you can look at too.
Good luck with your race prep and I look forward to meeting your team.