I've noticed that a lot of fulltimers seldom deploy their awnings, so maybe that explains the lack of responses. And another factor: tall motorhomes and fifth wheels seldom have a water drainage problem - the upper end of the awning is mounted high enough so there is plenty of pitch for water run-off. Trabel trailers, Class B and sometimes Class C's typically have the awning mounted lower and thus it is nearly level when deployed at a height that will still clear heads. Awning rafters are perhaps a help in that situation, providing some runoff assist.
Many of us use awning "de-flappers", clips that attach to the side edges of the fabric and provide some tension laterally. That is pretty effective in stopping awning flap in light-to-moderate winds. They also help keep a "belly" from forming near the center in a heavy rain. If the winds are too much for de-flappers and the basic awning arms, you ougth to be rolling it up anyway. NOTHING is going to keep that huge sail down once a high wind gets under it, including those tie-downs you often see.
In short, none of us think the support rods (aka "rafters") are going to be one iota of help in any significant wind. And it appears they would hinder you in attempting to roll up the awning if a thunderstorm suddenly appears.
I got a ladder and went back to try to raise the awning. When I released the pull the wind started to lift me off the ladder! It took about 10 minutes before I was able to get the awning back in place. Now imagine trying that with the big awning!!!
