It needs a pretty sturdy connection. The tension you put on that strap is what determines how floppy the fabric is in the wind. I've no idea how to measure such a thing, but think in terms of the kind of pull you use tying down a motorcycle to a trailer.Wondering how much leverage it needs - it would be easy to add a third awning bracket to a corner of the Horizon, perhaps on the opposite rear of the main box if it cleared the tent.
I have one on my base camp trailer which has also been changed over to have a globetrotter tent. I made the mount adjustable so that it is lower for travel and then high enough for me to stand under when deployed. I think that the extensions or side would be a nice finishing touch but they are nearly $200 per section.
hmmm, perhaps in Australia. Foxwing extensions are only abt $80. Example: but this seems to be a common price.
http://www.racksforall.com/rhino-rackfoxwingawningextensionpiece.aspx?CAWELAID=484813192