Have you guys used any bags from this series? More specifically, the tank bag? I daily my F4I, and 4-5 days a week I've got either climbing gear or school work that I need to lug around with me. If I need more room on the bike, I'll just get a rear seat bag as well or even saddles if I want to go nuts. How secure are they (for riding and "theftiness")?

Any other suggestions? Go cheaper? More expensive?

TIA