Hard pedal

Make sure the calipers are reasonably centered on the brackets. It is possible to have just one side doing all the work. That will make crappy stopping power. Did you remove the residual valve from the rear port that supplies fluid to the discs? Did you adjust the pushrod to make sure the compensating port is working? If the C-port is not allowing the fluid to return, the pedal will get harder with every application and the brakes will not release. If the calipers are also not shimmed correctly, then your situation makes sense to me.

Some pics of the assemble Scarebird set-up might help