Jason,

I have had good luck using regular c clamps and spring clamps where the most pressure is needed or just evenly spaced where no special force is required and then fill in the gaps between those with as many home-made pipe-clamps as will fit.  That way the factory clamps hold everything in alignment and the pipe guys give you the squish in between.  You do know I presume that the first rule of boat building is: "there are never enough clamps!!"

Good luck, Paul

Check your local dollarama (dollar store), mine has clamps, the spring clamps were not big enough, but they also had little bar clamps, at a buck a clamp goes a long way.