I didn't go forward with my plan to use the wire rack.
One professional brewer I sometimes hang out with pointed me to a very good reason that put a halt on it for the time being. I hadn't thought out the exhaust and had no "hood" to use with the shelf on the other side of my kitchen. I don't have the option to brew outside right now, so that pretty much nixed the idea for now.
The muffler clamps are a good insurance, and I agree I wouldn't put any hot liquids on there without insurance. I think the plastic wedges that support the shelves probably are not at risk below 100 C anyway, and if you don't see any evidence of melting that is reasuring.
So its been a while since I entertained the idea, and now I am thinking:
If I use the shelf to set up the burner, HLT, Mash etc... whats stopping me from building an exhaust hood ON the shelf too!? Nothing! I can just run some flexible exhaust duct from the top of it out a window or over to the stove-hood (maybe thats better to handle the condensation than the side of the house above a window). A little aluminum sheeting would do the trick I guess. I wouldn't want to use anything that rusts...
Not going to do that just yet, but gets me thinking...