I learned an odd thing when scumbags broke into my garage and stole my bike. The bike was hanging by the front wheel from a hook in the roof. In order to get it down, you had to handle it just right or the weight and awkwardness of the shape would cause you to lose control of it and bang is on the ground and whatever else was around it. This made noise.

When the scumbags were in the garage, one was lifting my car's CD player while the other focussed on the bike. The guy dealing with the bike must have made a lot of noise because the guy going for the CD player left without taking any of the CDs (easy to fence) or anything else.

This showed me that noise is the worst enemy of the burglar. Thus, what you might do is hook up a noise maker that goes off when someone takes the bikes off the hook. A bell or electronic alarm might be all you need.

I like leaving other, cheaper bikes unlocked to give them something to steal that you don't care about, too.

Ray