Auger flight size

[windseaker1]

Here is attached problem. We are very limited on space. Input will be air blown cement, out put needed is 2.5 tons per hr. A debate is on about useing a 6"Dia. Starting from left with a 4" flight and 6" flight at end of auger#2. Auger #1 is 6" flight at 1 to 1 pitch.
Auger #2 is trough, Auger #1 is tubular.

Any tips on the cross-over augers(Auger#2 delivering to Auger#1) is next question.