Hi Alan, all Your secondary is almost a dead ringer for mine, take a look at my toroid at http://www.geocities-dot-com/CapeCanaveral/Runway/3589/base.html This is 51" by 10", and is of the type you are describing. I have two others, one is 24" x 12" and one just being finished that is 38" x 12". I find that they work very well. Best Regards Robin <snip>