They look suspiciously like V brake levers to me - unless they are the type you can switch the travel setting on then I'd try some levers designed for cantis and see if that works better.
Well, I've gone and bought bargainous Shimano Deore V brakes so will be going that way. I think getting the pads to hit the rims properly might also help a lot. These frogleg brakes have no adjustment in that regard.
Got the Thorn on the road, rides beautifully but the brakes are woeful.
They are frog leg cantilever brakes, seems like no amount of adjustment can get the pads to contact well with the rim.