Configuring port channels on S5248F-ON switches

I'm new to using Dell switches and am a little stuck trying to configure a port-channel between a couple of ports on VLT connected S5248F-ON switches, being used to connect a couple of ESXi servers and a SAN.

I need to configure a port channel to use ports 15 and 16 on each of the two connected switches, to connect to another pair of S5248F-ON switches with their own couple of hosts and SAN. They are effectively two separate sites, so i want to connect a link from each switch in each pair, to each other switch in the other pair.

So basically the following connections:

site1-sw1 to site2-sw1

site1-sw1 to site2-sw2

site1-sw2 to site2-sw1

site1-sw2 to site2-sw2

My understanding is that i should create a port-channel on each switch. But should i be using the same port-channel and channel-group numbers on each switch, or should they be different? And should the numbers be chosen arbitrarily, or is there a relationship like there is between port-groups and physical port numbers?

For example site1-sw1:

int port-channel 10
vlt-port-channel 10

int ethernet1/1/15
channel-group 10 mode active

int ethernet1/1/16
channel-group 10 mode active

Then on site1-sw2:

int port-channel 20
vlt-port-channel 20

int ethernet1/1/15
channel-group 20 mode active

int ethernet1/1/16
channel-group 20 mode active

Thanks

RJ