I have also heard of people buying an AR15 handle rail and using the slanted profile to better fit the rail on the Arsenal front hand guard. Not sure which method I am going to use, I have both a regular rail and the AR15 style handle rail waiting for me at home. Will post pics when I get it done!
Here's the AR15 rail BTW
http://www.mississippiautoarms.com/ar15m16-carry-handle-mount-black-tapco-p-1399.html