I bought a Heartland Sweetheart cookstove this past winter, and will soon be installing a chimney for it. they sell a rear heatshield for about $225. Seems pretty steep. Does anyone know if it's possible/safe to fabricate your own heatshield for this? Is it just a matter of cutting some sheet metal to the right dimensions and then attaching it, or do you really have to buy the "official" heat shield? Supposedly, the one they sell is "insulated", but I can't see any difference between the function of this and one for my Mansfield, which is just a sheet of metal.