6061-T6 is good aluminum, but it is hard to bend because if is already tempered. To get a good bend in 6061, your bend radius should be a minumum of 2X the material thickness, 3X if you bend to 90 deg. Even then you will see stretch marks.

You can go to www.mcmaster.com to order aluminum if you do not have a local sullpier. 6061 is plenty for most rc planes.