Quarter Panel Patch- Stupid Question

I need a lower quarter patch on my 74 Swinger- picked up a cut from the Carlisle this summer.
It has the quarter panel skin and the trunk extension still attached together. Should the two be separated and just patch the quarter or cut the existing quarter and extension- Have it welded as one piece? Any benefit to this method- someone mentioned to me it may prevent any warpage on the quarter?
I'm no expert but the few quarters I worked with you better off to leave the original quarters on and just weld in patches, a good welder can put that in with very little mud and warpage ,