Today I replaced the burnt out fet on my RX-18 hoping to have it up and running again.Unfortunately there must be some other damage to the board as it burnt out straight away again.So it may be that when these boards blow it's the small 8 pin fet that shows physical damage but something else is being damaged that is not obvious from just looking at the board.Which also may mean that stacking these fets may not help either.
I will get a new RX-18 and do what others have done before me and fit a fan and some quick blow fuses.
On a side note,I've just blown an RX-14.All I did was run the tank backwards and forwards a few inches on a smooth surface,turned the turret,turned it back,then the RIGHT track on it's own started turning and I could smell burning.Turned it off and opened it up and found what I expected,a burnt out fet.However it was on the LEFT side that had blown.Strange,it was not jammed or obstructed in any way,it just decided to drive the right side and burn out the left all on it's own.
I seem to be getting good at burning out fets,it's all I can smell at the moment

Steve.