Another option to the Mantis Claws is using either a short or a medium RAM arm and two 1.5" RAM balls mounts. The advantage of the RAM mount is that the ladder can have both feet on the ground, even when the ground is uneven. Plus, it will only set you back $50! Add 2 more ball mounts and you can move your ladder to any side.
RAM balls come with different shaped bases, 1/4"-20 studs, or T-bolts. The latter would be a really clean looking mount on the V1/V2 side channels. The plate on the stainless steel T-bolt is slightly smaller than 1/2" x 1". If necessary, file down the sides of the plate to fit the RTT channels.
I posted some pictures of mine (w/med. arm) that I mounted on my Front Runner rack in the SuperLite section.