This might be a dumb question but does it make any difference which barrel is on top? Tradex has a Brno ZH104 and its one of the only ones they have with the rifle barrel on top.
Most others have the rifle barrel on the bottom because they hinge and lock up under the bottom barrel, so having the higher pressure of the rifle barrel closer to the hinge pin means it places less stress on the locking mechanism. The Brno 100, 200 and 300 series have a massive crossbolt at the top, and a hinge up at about the midpoint between barrels, so there's no benefit to the rifle barrel being on the bottom. Having it on the top means that it is closer to the sights, which some may prefer. Having tried both configurations I think it makes little to no difference to the handling and shooting whether the rifle's top or bottom. .
