The only prob I found w/ this method is, if you heat up the neg terminal too long it can desolder the legs on the components of the existing protection board. and I had sanded the coating off and used flux.
happened to me on my latest saber, luckily I had ordered a 7.2 pcb not knowing the cells were already protected, so I took the cells apart and removed the existing PCBs and built them back up w/ the 7.2 board.
but I have a saber from Eastern that Im sure he used this method on and they work perfectly.