This goes for all people who want to have a look at improving their technique....
Google "Danny Ching". He's the current Team USA DB coach and the world number 1 in the Outrigger Canoe (OC is a great cross trainer as it's the same stroke as DB). He brought USA from nothing in the world champs in 2005 to 4 golds in 2007. He paddles OC1 - A LOT - so knows how to make the boat move.
In particular look at his body position, vertical. He isn't lunging forward like a lot of people do. He's getting the reach through rotation of the core and the power from the large muscle groups - abs, lats and legs. If you're having trouble with the fast rating, it's probably due to the fact that you're using too much bicep/tricep and shoulders. These are relatively small muscle groups and will tire very quickly, which means you'll slow your rating, or shorten your stroke to compensate. Abs, abs, abs and more abs.
Look at how his top hand never goes lower than the sternum and he's getting a full catch before he engages the power. Crunching down with his abs at the same time kicking with his legs.
It's also a great learning tool for teams who can't train 5-6 times, if you can't train hard, train smart.
Here's a plug for my team....want to try outrigger? Singapore Paddle Club offer introductory lessons, drop me a line for more info!