Flush ceiling extractor -- installation

How are these normally fixed, assuming hidden fixing?
In our case, an Electriq extractor, also sold as Innocenti, has brackets which assume that it would be fixed to the ceiling structure, with a false ceiling about 300mm below. Trouble is, it assumes that there is access to the false ceiling void: we don't have that. All the fixings are on top of the unit, and once it is pushed up into the hole - no access!
Do I need to fix this and then re-build the ceiling around it? Sounds crazy, then I will need to destroy the ceiling to get the unit out, or access the motor if maintenance is required.
(Or take up the carpet and make a big hole in the room above???)
Thanks...

 

You make connections before installing in your hole.

 

Not sure if you've undestood from my description: the situation: the mounting brackets bolts to the unit at one end, and the top of the hole at the other. So how to do that before I put the unit in the hole...because the unit has to be already in the hole before I do up the bolts.
Or have I missed something obvious?

 

Instructions? You would normally access the fittings thru base after removing the filter/grease trap.

 

That's what I was expecting... but the instruction manual only covers installation on the assumption that you have access to the top once the unit is in place.
The centre part, with grease filters, doesn't allow any access at all, unless disassembled from the top, so that's a non starter.
At either end there are light panels... these panels come off and allow access to the top. There are some holes, not fixing points exactly but I could fabricate something to spread the load a bit and bolt the unit up like that. That's my reserve plan ...only done one extractor like this before and that had access from under once the filters were removed.
So reason for my post was just to find out if there is some magic trick which I don't know about.

 

So what do the fitting instructions say?