No downdraft actually works. Save your money and put in a real vent fan.

Thank you, we were looking at extracting outside not recirculation, do you still think best to vent out on a wall extractor instead?

Fumes, smoke, heat, vapor - all of that rises. So a downdraft is trying to counter physics and, therefore, will never be as successful as a hood that covers the cooking surface.

This is why it's ideal to have the hood extend 3" beyond the cooktop on the sides. It's also why a microwave/vent combo, which doesn't cover the front of the cooktop is less efficient.

Thank you, think I’ll save my money

And a Best Cattura is even better. But it isn't close to matching an overhead hood. If you can include a wall mounted overhead hood in your design you'll have the best performance.