The Arm is a stunningly beautiful and very small river. Most people who camp at Arm will see the falls.
The section from the falls to the bridge has benn done about 4 times, most in inflatables, and once in little boats, this is continuous tricky g2 with a few logs, strainers and overhanging branches
The section above the falls contains steep g3/4 stuff (see pics) and culminates with a g6 (unshootable) this section has been done twice, and is a lot of effort for little rafting due to the walk in, and the (very uphill) walkout. it takes something like 5-6hours to do 3 kilometers including the walkin/out.