Just keep the flame low, very low...and you should be fine. I tried the insulation route, but with direct fire I don't really see it as being necessary. Low flame and constant recirc holds the temperature I need. One word of caution, watch out for the hole in the skirt by your valve. Flames, or even heat, could come out that hole and burn (or melt) the insulation.
Other that than, give a shot with a close eye the first few times.