ah ha, light is dawning!!!!! This is done the same way as the Daleks bum!!!. I did that on 4 needles and then cast off on 2 but I think I will need to think about it some more. ......... ,,,,,,hmhmmmmm It depends on how many sts you have started with. Once the pattern is set then it should become obvious where you put the dec but as you are decreasing it will alter the line of “bumps” anyway and short of starting it myself I am not sure what the answer is other than doing a PLAIN bottom. Sorry if that is no help, maybe someone else can put you right.