Does anyone know how it works if you purchase the Bittware version since the defaults is w/no memory installed?  Can you purchase your own DDR memory to install, and if so what kinda?

The following is offered from Bittware, but what is recommended?

R4 = DDR4 16GB RDIMM
R5 = DDR4 32GB RDIMM
R7 = DDR4 128GB RDIMM
L5 = DDR4 32GB LRDIMM
L6 = DDR4 64GB LRDIMM
Q4 = Dual QDRII+ x18 144Mb
Q5 = Dual QDRII+ x18 288Mb