Roadwasher,
If you go for the Triumph bags this is what the brackets that come with them look like:
Judging from what you said about a "one screw" procedure to remove your seat I would guess that you have a Speedmaster, so the spanner GinaS mentions above is not required.
The yoke adjustment procedure is as per GinaS's description.
I am actually going for the K-Drives myself as my journeys are somewhat long and mostly 2-up (although I have another bike for this purpose) and I require more space (well, not me exactly, but you get the idea

).
I also like the lock-on/lock-off feature without having to install brackets and modify bags etc. (yes I know, I'm lazy

) and they seem to be big enough.