Hi Jeff, thanks for the reply.
Ah yes I remember reading about the mesh screen debate a while back.
I have the roof holes already covered with aluminium fly screen. Inside the roof cavity is just restricted empty space. Pictures as below:
Would I therefore get the same result if I just put a hive mat either on top or under the mesh screen?
Also with your idea, wouldn’t the bees then have access to inside the roof cavity and therefore a possibility to draw comb? Apologies in advance if I have mis read your post.
My rationality for the keeping the screen was due to ventilation. We’ve had consistent 40 degree plus days so I wanted heat to vent out yet not allowing the bees to move up, also the fact I have a black roof. (I painted it black to absorb more heat during winter when the sun is out because the hive sits under shade for most parts of the day) Apologies if this all sounds confusing. When I get an idea sometimes it can be dangerous 
In regards to the solid bottom board level, it shouldn’t be a problem as I have adjustable legs. I made the stand out of an old Jarrah fence that a Marri tree crushed at mine!
