That has quite a "sail area" so will require some decent tie down weights etc to resist uplift should you get a decent gust or rain squall.
The other matter to consider is that being in Cairns you can get decent rainfall in a matter of minutes, enough to pool on the flat tarp roof even destroy it. Perhaps consider adding a third roof member to create a ridge and fall so that rainwater will run off and not pool.
A public liability insurance nightmare imo. If it can happen it will happen. :rolleyes:
ps what do you do to secure the containers when we are on cyclone watch / warning?
One suggestion re a roof would be to re orient the containers 90 degrees and place them one car space apart, or leave them in the current position and move the light coloured one to create a work space between them. It seem the loss of parking spaces isn't an issue. The containers then become the walls and roof support with more than enough weight to hold down a semi-permanent roof or even a permanent one. It also gives you more options for shade roof materials and would be more acceptable to an insurer - well if you can ever satisfy them that is. :roll: