Hi dougpenny, The memory configuration looks fine, ftp.dell.com/.../poweredge-r410_Owner%27s%20Manual_en-us.pdf page 120 Fully populating with identical DIMMs is a supported configuration. 
I am in the process of upgrading the RAM in our dual-processor R410 and would like to verify the configuration before buying the memory. If I am reading the documentation correctly, I believe the following memory configuration should work giving us a total of 124GB in Optimizer mode. using dual-rank 16GB DDR3 RDIMMs (Kingston KTD-PE313LV/16G)
R410 Memory Configuration Help