Instead of bicycle chain, use a length of 530 motorcycle chain. This stuff is heavy and a bolt cutter WON'T get through it. The only way is using an angle grinder to grind off the heads of one of the rivets. To anyone who has changed a motorcycle chain without a master link, hardened steel isn't easiest thing to get through. No pry bar or chain break is getting through that easily. That being said, I ride a Charge Spoon saddle which is about $25, so I don't go out of my way to obsess over saddle security.

At this point in time, I'm only riding recreational and don't lock up. When I was in college and riding to campus, I'd pick the first light pole outside of a busy lecture hall and lock it to that. The constant foot traffic made it a conspicuous target and I never had a problem.