Trivets are a mixed bag as there are several styles, sizes etc. I have found the thin wire ones the worst and use the disc trivets with lots of holes in it instead, depending on what I am cooking as to whether I cover the trivet with alfoil or not use it at all.
@ OD I have just had some stainless steel trivets laser cut and fit the 12 camp ovens just right, Iput my meat in an Alfoil tub on the trivet and cook that way with a half cup of stock to help it fall apart. If anyone is interested in the trivets just send a PM, should be featured in next issue of 4x4 Australia Mag
Mine is the solid stainless number, very affordable