i use the sections from foundry 4x4 on ebay used them before and just had another set delivered today they are long enough to do right along the botton and about five inch up each side of the door if you are accurate with your cuts,
when you cut the mitres the bit you cut off becomes the right angle for the other door if that makes sense
only bit to watch is if you come up as far as the hinge bolt holes they are brazed in place