I use a 240 cm paddle and it does drip a fair amount if I leave the blades unfeathered (blades at the same angle), so I don’t think a longer paddle is necessarily the solution, but it could help. I feather my paddle to 30 or 60 degrees so the top blade is flatter when the low blade is vertical in the water, and then water doesn’t run off the top blade quickly enough for it to drip – it makes a huge difference. It takes a while to get used to a feathered paddle, but it’s well worth it – not only to reduce the drips, but also to minimize wind resistance when paddling into a headwind.
Another factor is the blade shape – a wider whitewater style blade seems to help prevent drips from falling in the packraft because there’s a low spot on the edge of the blade closer to the tip, so drips tend to fall from there instead of running down the shaft as it would with a narrow touring blade or a Greendland style paddle. My go-to paddle doesn’t need drip rings because it has fairly wide blades so water never runs down the shaft.
I’m not sure if I’m explaining this very well – if not, let me know and I’ll draw some pictures.