Welcome to the Shack!
More sheen equals less TiO2. Less TiO2 is not what anyone really wants. You'll have to experiment some with the paints available to you in Sweden to find the happy medium. We did it here in the US and it's been done in Australia and the UK as well so I don't doubt you can figure it out there in Sweden.
How exactly are you adding your sheen? Are you adding polyurethane? Or are you just buying a paint with a higher sheen value.
Flat paint works fine here. Harpmaker has used flat paint in all of his tests.
Keep in mind we don't check on AVS anymore. Last I checked though the view count surpassed all of the 'advanced mixes' within a month and a half or so!
And we didn't even have to keep going back and pimping our own threads like some do!