Are ITM TT levers OK with caliper brakes?

Ooh_Gravy OK, this may well be a stupid question but I recently bought some of these thinking that I'd just install them in my nice new bullhorns and use them with my old road calipers on my SS. But having tried them tonight, they don't seem to pull far enough for the brakes to bite.
Now, when installing brakes, are you supposed to take a pair of pliers and pull the brake cable down before you fix it to the caliper? Or are they designed for some sort of specialised short pull caliper?
Thanks.

I have these on my SS with very old brake calipers and they work just fine. The cables should be pulled tight before you tape the outer cable to the handlebars, otherwise they feel a bit mushy.