I like the look of bags on the bike... I've seen lots of single bags on old pics of bonnies

I recently purchased some large angled throwovers.

Two quetsions:
Is it vital I purchase the support that bolt on?
Can the pillion seat be removed and placed over the center of the throwover?

The idea of throwing the bag over and riding is giving me visions of the bags blowing off the bike at speed. As you can tell I'm new to saddlebags :P