Save yourself some money and just raise that one up a foot.
The height recommendations are for minimum height - You can get away with much, much higher - the technical drawings will give you an idea of high high you can go without having to do weird things with ducting.
If I could I would, the external vent/ actual hole is straight out from the top of the hood, very bottom of the duct. The ducting/boxing above is primarily aesthetic. Could probably squeeze max 100mm. Could obviously patch, move up and redrill, but not sure I really fancy doing that.
Save yourself some money and just raise that one up a foot.
The height recommendations are for minimum height - You can get away with much, much higher - the technical drawings will give you an idea of high high you can go without having to do weird things with ducting.