That's one way to use up all that space on the front inner fenders!
*I would never have thought about storing anything there.
I am planning to build a cross-bed tool box and carry an extra hydraulic floor jack. The wider base should be safer than the pedestal models although I still have the original jack (dad said he used it one time, helping another guy). I'll carry wood blocks too if needed.
In winter I carry the same sort of hydraulic jack in my car as it's the best way I have found to put tire chains on. With that jack, I can do both wheels in under 15 minutes. Another benefit is the long base allows much more stability.
Here is the sort of jack I am talking about.
http://www.northerntool.com/shop/too...5429_200345429