I'm no fan of Pins and Clips...
its a matter of personal preference and all the systems have their advantages and disadvantages - you just gotta weigh them and decide. I've known some great boaters who used them, including the most solid boater on a recent Grand trip. However, the worst wound I've ever dressed (48 stitches, internal and external) was a result of someone falling against that setup.
Is it too late to take the stirrups back and get some oar locks? If you stick with it, make sure to cover those razor blades - I mean hose clamps - up well with tape, and also be sure the rubber cover is installed correctly on the top.
Nothing in the world is more yielding and gentle than water. Yet it has no equal for conquering the resistant and tough. The flexible can overcome the unbending; the soft can overcome the hard. - Lao Tse