Don't make stubs... why? It makes a messy job having the extra welds and most car headers have no space for tubes to go straight out from the ports.
I shape the tube, usually a J bend cut in half, even on the curve, quite easily with a hammer and vice. Hammer one corner to a 90 degree point, check to see if the tube aims where you want and adjust the corner up or down. The tube can be squeezed in a vice to flatten the sides and then tap in the ends, put them in the vice and flatten (edit, the C clamp idea is better) and fine tune the shape by hammering over the edge of an anvil or steel block.
By the way Turbohunter, where did you get those nice looking flanges? Many aftermarket ones come with way too small ports. Yours is what they should make.