SSBC disc brakes won't stop

Those speed bleeders, can you close them and run them or do you take them out after its bled? Seems like taking them out after its bled is inviting air back in. Disk brakes require more fluid, just look at a Disk/Drum M/C. I bet a larger bore will help. I would be interested in the rear disk choice from drum. Fade resistance? Much easier to work on but thats about the only positive I see in running them in the rear.