As Kev said, It will be better to cut through the welded joint of the tube to get to the cat, will be better for two reasons:

1.- Better clearance to get the cat out.
2.- You can weld again the tube and nothing is noticed.

I remeber seeing some pics in the forum of a dismounted stock exhaust, can't find them now. If I can get some second hand oem cans I will try to do that, remove the cat and doing some things more. But only on cans I can break or loose, oem mines have to be ok for technical inspection.