Recheck the radiator cap, pressure test the radiator, recheck all hoses and clamps, run another block test. It is possible to have a head gasket leak without tripping the chemical test. Take a small sample of the transmission fluid, and see if any coolant might be in it. Remember this: New does NOT equal known good. 

Because you don't say how much coolant you're losing, over how many miles or days, it's hard to get more specific. 

I will fill it up and within minutes and or even miles the low coolant light comes on I feel like it's when the thermostat opens is when the coolant seems to just disappear and both upper and lower radiator hoses remain rock hard but one thing I do notice is that the overflow tank remains full during all of this 

If the light comes on when the tstat opens then maybe you still have air trapped in the system. Did you replace the rad cap?