I can let you have 3 lengths, I think they are about 12" (maybe 13" - I think that was standard).
However, silver soldering 1/16" material may be more tricky than you think, particularly if you need to avoid any warp at all! Use the lowest temperature silver solder you can lay your hands on and heat gently. Might be best to use a solder/flux paste mix and heat the whole assembly indirectly.
ChrisH