Flycutting a Saddle

[Toolmaker51]

That method works correctly, there is a preset to streamline the setup.

Measure shank diameter. Lay the cutter shank horizontally in a Vee block, lay on side to get cutter slot parallel, and clamp. Re-erect Vee block.
With height gauge, touch off shank diameter, to realize centerline.
Adding desired radius, set height gauge to that dimension. Raise cutter in contact to gauge foot, viola'!

Granted, it works best to have two cutters, one a rougher. We saddle weldments this way frequently, especially square/ rectangular tubing for round stock.