Milling Carbon Fiber Composite

I showed you how I clamped down that 6" x 6" x 3/8" plate of material.  Then I used the 1/8" carbide end mill to slice a 1.125" x 6" slice.  I do not think that I clamped it down right enough or perhaps 1"/minute was too fast and it rotated slightly on the table.  So I had to the workpiece (both the 1" slice and the remainder) vertically in the mill vise and square both of them with my 3/4" HSS end mill.  I cannot see or feel that it has lost its sharpness, but I think that for these sort of facing operations, I should buy a large diameter carbide end mill.

Did the 1" slice come out a size that will make the dust caps (really fillers) for the 1" rectangular tubes.  It slides in either dimension with enough pressure that it will stay in place while I turn 6-32 screws into the edges.