Upgrading memory on a R510

Greetings -

I have a R510 that currently has 32GB of memory with 4 GB in each of the 8 slots.

I'd like to upgrade it to at least 48 GB but, like many others, I'm a bit puzzled by the various configurations and would like to avoid purchasing memory.

My understanding is that -

• Both banks must match.
• The DIMMs in slots 1 & 4 (channel 0) must match (both banks).
• The DIMMs in slots 2 & 3 (channels 1 & 2) do not need to match (except bank to bank).

Is my understanding correct?

Thanks in advance for any and all input.