so, can you get a good seal without the stove rope around the lid?
I've now modified 3 types of lids for use on a UDS.
Weber 22.5" Kettle lid:
Even though I got the entire grill used on Craig's List I couldn't bring myself to mess it up bending it, so I cut off the "lip" around the top edge of the drum I planned to use, the Weber lid sealed up acceptably. It leaked a little bit so I cleaned up the lid and applied about 1/4" bead of high temp silicon sealer (wood stove sealer) around the step down lip of the Weber lid. The top edge of that UDS needed to be sanded and shaped a touch to insure it wasn't sharp enough to cause harm when reaching down into the UDS, otherwise it was a simple fix. BONUS? 15.00 for a replacement cooking grate for the Weber and I gained an entire functional Kettle out of the deal.
Wal-Mart 22.5" $40 cheapo:
I pillaged this for a variety of parts. I flattened down the entire lip around the outter edge of this lid. It rests flat on the open/rolled edge of an open-ended drum. I'm still in the process of adding this to a flat-top UDS, I'm modifying the hinges slightly and then will be using thick, round flexibe wood-stove rope/seal to make it all fit snug.
Big-Lots 29.00 cheapo kettle:
I snagged one of these because initial measurements looked real good for a nice fit. I ended up having the do some bending around the outter rim to make a good, stable fit. This cause the enamal paint to chip a bit, no worries, sanded and sprayed it flat-black along with the UDS. The drum I used was a sealed drum, so I opened the top can-opener style, then used an angle grinder to make the folded/rolled edge fit with the Big-Lots lid. It didn't seal up very well until I added a 1/4" bead of high-temp silicon sealer, but now works wonderfully.
Each of these examples were different drums, different lids but it all worked out with minimal effort or modification.