From my expierence I find that using a 3 to 1 ratio seems to work well. For example, during veg using 3, 6500K lights and 1, 2700K light..... Or during flower using 3, 2700K lights and 1, 6500K light.
Right now in my flower room I have 4, 13W, 2700K CFL's..... 4, 26W, 2700K cfl's..... 2, 26W, 6500K CFL's..... And a 24in, 20W UVB flourescent tube.....
From my expierence I find that using a 3 to 1 ratio seems to work well. For example, during veg using 3, 6500K lights and 1, 2700K light..... Or during flower using 3, 2700K lights and 1, 6500K light.