Combination microwave in overhead locker

Looking at purchasing a combination microwave, to allow me to do a bit more than heat up food/ cook ready meals etc.
I’m in a DAF xf 106 superspace, and at the moment, my microwave is in the central cupboard above the windscreen.
Has anyone used a combination microwave in there?
It will be a small 20 or 23 litre one, so will have room around it. My only concern is the heat generated when using either the convection oven or grill part of it.
I also use a slow cooker.
Will be powered by a 3000w (6000 peak) pure sine wave inverter.

I don’t know about combination microwaves, but the Daewoo QT-1 seems to be the microwave of choice for many, as it’s compact but holds a full size plate. It’s also favoured by the boating and caravan crowd

Friend of mine runs in a 21 plate DAF with a microwave fitted in the top centre locker, it’s DAF branded 500w, he’s never mentioned any issues with it, I’m sure he said the manual states it can run for 30 mins with out starting the engine ( sounds a bit long, and what the hell takes 30 mins? )
I know it’s on its own in the locker as not much room so I guess a bit more room for the heat, which will be a bit less at 500w?
He just uses a conversion site on the internet to convert the cooking times to 500w and bingo.

I suspect that using a convection oven or grill for extended periods in the top locker won’t be a good idea, not because of the heat but the draw on the batteries. If you run the microwave you will only run it for a couple of minutes, whereas you’re going to have to run a convection oven or grill for 10,20.30 minutes to cook your meal