Thank you for your prompt and informative reply. I thought it might be the case that I would have difficulty registering as a corporate tartan, but it seems the best match category for what I want to do. "Fashion" doesn't really fit the bill, IMO, but I can see how that might be the best way to do it for now. When I'm ready to submit my application I want it be as correct as possible to help ensure that things go smoothly. I'm obviously new to this, and your pointing me in the right direction is much appreciated.

Whenever your software rewrite happens (I sense nobody should engage in breath holding in the interim) will existing tartan registrations likely be recategorized?

Slàinte!