Haven't tried the steel version but here are some pics of a cabinet repair using regular Knead It.
This area was badly water damaged and after removing all soft wood, there was not much left in this corner.
After the repair , I was able to lift the entire cabinet by the knead it putty. Strong stuff!

I think you probably could just fill and drill it ok (probably be easier) but I needed this hole to be perfectly centered so used the drill bit in a different way.
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Thanks mate,i'm going to try the steel knead it,i saw it at bunnings last time i was there,let you know how it goes.