Here are some thoughts:
– I think my oar lock formula may break down for really small and really big boats.
– I have that same boat and the distance between my oar locks is 60″ and the formula gives 8.15 feet and we use 8 foot oars. They work fine.
– Rowing these small boats always seems a little awkward to me compared to normal (13-18′) rafts.
– I think part of the problem is that your frame is a bit narrow for that boat.
– I also personally find cataract oars a bit awkward so you may like Sawyer oars more.
My best advice:
– Get the oars a bit shorter – closer to 7’3″ would probably help so they balance better.
– Try to have the oar handles touch or even overlap so the percentage of oar outside the lock decreases.
– I’ve never tried smaller blades to solve problems like this but I’ve talked to people who have and it seems to work.