Where are you looking to buy that light from, Quick Bloom Lights in Australia? And is that light a DIY kit?
Here in the USA, HLG is currently selling the HLG 650R. The Diablo board DIY kits are discontinued (the boards are still available through at least one reseller) due to the known board wiring issues.
For the light you referenced, they use a HLG-320H-C2100A driver but you won't get full power out of it with these boards, more like 270-280 watts. I would try to stick to the recommended 8 to 9 square feet for flowering.
Are the dimensions of your grow space flexible, or are you set on the 3.5x3.5ft. area?