I just logged in to this forum to request this exact thing.
1 byte is not enough. There is a real chance of the wrong XDF loading. At least 4 would be a lot better, or better yet, more. It's be great to just specify an ID in the ECU that's and recognise that ID in full.
I'm about to set mine up now with 1-byte values but I think I'll get false hits from time to time.