The instructions state a recommended height but some people do ask for them to be fitted higher. Main reason to make using hob easier, being able to see the back of the hob without banging your head on the hood if your tall. Never fitted one that high off the hob though.

This is basically what it says on the internet:- Re-circulating cooker hoods push the air through filters, these filters then remove any cooking smells before the air isreintroduced back into your kitchen. Most modernrecirculation hoods feature a basic grease filter as well as a charcoal filter, these work together to remove grease, food smells and smoke from the air. If your air is not able to escape in to the room as above, and it's fitted somehow differently, it may possibly be incorrect, you'd need to see the whole thing. However, rinq is correct, you shouldn't have a gap underneath and maybe air is escaping somehow to where it should not be.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiu4JzukrDrAhWCRBUIHY5ICbMQFjAAegQIAhAB&url=https%3A%2F%2Fwww.agaliving.com%2Fsites%2Fdefault%2Ffiles%2Fuser_guides_uploaded%2FAga%2520Oil%25202%2520and%25204%2520oven%2520inst%252004-07%2520EINS%2520510949.pdf&usg=AOvVaw3ivvnZjSvvpxNem9xVHPAO the above link (right click and open in new tab) should take you to the aga oil fired fitting instructions, page 4 goes into air supply and extractors

Thank you for the replies and sharing your experiences! It seems then it is possible to use this approach (although it’s still interesting whether this applies to any brand or not). I will try to report back if it worked with an Electrolux in our case or not. @LuxeLtd the kitchen looks awesome!