I know you have already done it and its mint, but do you not have this bracket? (the one myself and Arthur_T3 mentioned)
You can see the bracket on the back of the De-cat pipe, the CLOSEST bolt you can see. The bracket loops over the flange to the other bolt, then bolts to the chassy with a rubber mount. Ill get a proper pic tomorrow for ya seeing as the car will be on the hoist for inspection.
If not it must have been taken off and dumped Cos you shouldnt have needed to get one welded on. Never mind tho!