These ones from Acoustic Cycles look nice too. The ones my friend uses are a bit more in the washers and tape style. He showed me the difference inside the tube with and without the gas. I thought that was only necessary for titanium... not sure where I got that.
That looks good. Assuming you are also using the mill to cut the top tube and downtube where they meet the head tube, how do you jig it up to deal with the incline of the tube relative to the plunge of the cut?