Would somebody explain the term 'pack the Pixels'. Not sure I understand. Thanks --Greg--
I've not heard that term, but I'll take a stab at this.
Say you have 5 strings of 100 pixels in each string for a total of 500 nodes (1,500 channels). You'd typically set up XLights with three 510-channel universes to cover it. The protocol allows for 512 channels per universe, but most use 510 giving you 170 nodes per universe. So, node 1-100, and 101-170 would be on universe 1, 171-200, 201-300 & 301-340 would be on universe 2, etc. Basically a contiguous 'pack the Pixels' use of channels. Forgive me if my math is off. I'm doing this in my head.

Another way to set it up is to use 5 partial universes with a string on each universe. So node 1-100 on universe 1, 101-200 on universe 2, etc. This sounds so much easier doesn't it?
With 500 nodes, it really doesn't matter which way you go, but when you multiply that by 10 or 100 or 1,000, the universe count rises quickly. Older controllers only support a handful of universes so that almost mandates 510-channel universes unless you have stacks of cash for more controllers and network switches.
If you add Falcon Player (FP) into the mix, you have to mirror the channel setup in FP. It's just easier to remember 510 for every universe (and sort out the channel-to-pixel connection at the controller) rather than use a non-standard amount. 300 here, 60 there, 150 over there, etc.
You might think well, I could set FP for 510 and it still won't be a problem since I've separated each string on a separate universe. True, but then your pushing a full universe worth of data over the network even if you only use 1 node in the universe so network saturation becomes a problem as the number of universes reaches a certain point. I forget what that limit is. I think it's been tested to 64.
I hope this helps.
Jeff