I guess I'm an expert, especially since I got audited by the state for taking the exemptions! It sounds like you have a pretty good handle on what you will want if ever audited:
The fuel log, excellent idea, these people love paper work, and you want to be able to shovel it at them by the truckload.
Absolutely required is the paper receipt that comes out of the fuel pump, not just your credit card receipt, guess how I found that out?
This may be overkill, but taking a date stamped picture each time you fuel, showing the actual fuel hose going in the actual airplane, and being able to match those pictures up with your hand written log plus the receipts and you'd be golden
A nice lady named Nancy is you would be dealing with if audited, and I'm not being sarcastic, she made "getting caught" as painless as possible, and educated me on the importance of keeping the paper trail. I didn't in some cases (I was/am also claiming a deduction for my off road use of diesel while operating my crane on the job site) and had to pay a small amount, less then $200.00. I was happy to wrap it up for that amount, and got educated in the process, now I have my ass covered 6 ways from Sunday. Most importantly, I was able to prove to her satisfaction that I was a dummy and not a criminal, big difference. No fraud on my part in other words, just sloppy record keeping. A few weeks after we finished up, I got a further query from the state tax people, asking how I would rate her job performance, I gave her a A+ and meant it! They let me slide on the previous years and just "got" me on 2011, fair enough.