I have done my share of small boat making/repair and find cloth is a better finish that mat, but both will work. Mat has random fiber and may, after a year of use expose the fiber ends to your hands. Be sure to use a finish resin, which has wax added, to give a good cure. If the tube is to be painted than it will need sanding and wax removal. The wax gives the glossy finish and aids curing. I am sure the sona tube will need body putty to fill the seam and some imperfection.
I'm not sure, but I would think that a layer of matting and cloth each would be more than ample. The bolt holes won't be stressed in bearing so tightening should be your only concern. Lotsa Luck,
Bob
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