1949 AJS model 18 Tool box bracket

[Invicta]

Having at last got a piece of steel to make up the small bracket the connects the top rear corner of the tool box to the rear mudguard , can anyone tell me how big the joggle should be? I have one of the later straight brackets to get the hole positions right, but the correct one with the joggle in is just not available, hence I am making my own. Looking at photographs it is very difficult to judge, but it looks to be about 3/16"