Unsupported Oak Worktop

Hi,

I'm installing a 27mm solid oak worktop as an island. It's 1720 long and 820 wide with 350mm units at each end and there is a gap in the middle to sit at of around 990mm. I've put 1 supporting leg in the centre of the gap and want to know if this is enough to stop it bowing in the future or if I should be putting some additional strips of wood on the underside for support?

Thanks