Here are my two cents worth, based on having a cased awning
for 20+ years.

1 cent:  Stake downs never work.  I tried for many years,
not wanting to mount the brackets on the side of my van.
Finally, I did, and found it is much more stable.  Triangle
strength.  My awning has been up when storms blew through
and--an old bracket broke but not the awning.  Yes, the
legs are in the way, angling down to the side of the van,
but it is worth it for the stability.

2 cent:  I started with three brackets--long before GoWesty
made any.  The gutter rail took a beating--this on a Westy
Syncro that likes rough roads.  Finally, I looked carefully
and--thought!  The side of the bus, the gutter, is not
straight, it is bowed out slightly.  The awning case is
straight, so flexing it to fit three brackets just adds
stress to the brackets and the gutter.  I switched to two
brackets, and then to GeWesty's with the Rivnuts and I
now think that is the only way to go.  Two brackets with
Rivnuts holding them from flexing out.

Richard