After you take the bow out of the clamps, lay the riser on it's side and lay the bow over top of it and trace the curve of the bows riser onto the riser then cut the riser out and use hand tools to get a nice tight fit. I use a 13 inch riser but you could go a little shorter, maybe 10 at the least. Leave the limbs from the flares out to 6 inches the same width as the flares themselves,that strenthens that area a little.