Apologetics for the late response but this has just been brought to my attention.
This DA is a very significant increase in site coverage and far exceeds the 50% allowable and should be rejected on that grounds alone.
To approve this DA would be setting a bad precedent for seni-detached houses in Haberfield, that they could virtually cover the whole block.
The high ridge line would cause significant overshadowing to a neighbour who has lived at that address for about 50 yrs. It's not just that someone can buy the block next door and build something that will deprive any resident, let a long term one, of the sunlight they should continue to enjoy.
It appears the proposed extension is two storey which I understand is not allowed in Haberfield