PE R710 Memory Configuration

I have q-4 16GB 4Rx4 PC3 sticks and q-12 8GB 2Rx4 PC3L sticks. Is it possible to intermix them on a PE R710 Server? If so, what is the proper install?  I tried putting the 16GB sticks in slots 1 and 4 (both banks) and the 8GB sticks in slots 2,3,5,6,8 and 9 (both banks), but it doesn't work. Any help is appreciated!!