Can it be done ? Has anyone done this ?
My rear window has a pentagon anti shatter film on it and over the years a bit of moisture has crept in making it a long process to clear.
Since swapping over to JDM folding mirrors I have the same issue with the wing mirrors (taking too long to clear) .

Any advice on this ?
Can the wattage be increased to the demisters ?

 

Not easily. You'd need to lower the resistance of the demister circuit or increase the voltage supplied to it.