SH4 Editor query - Generic ship desig

[HMCS]

How do you determine which ship is the GENERIC escort? I was planning on editing convoy compositions for TMO and RSRDC and thought about tweaking the difficulty by assigning different ships to certain convoys.

Thanks for your help!

EDIT - I'm thinking that it's a random selection - looking at the editor I see that I can pick a specific vessel and assign a crew quality to tweak difficulty.