I went through this same scenario a year or so ago. After my 3rd receiving of the dust cover from burn marks I decided to so something about it. I tested a bunch of material and did not find one that did not mark with a magnifying glass.
I ended up making patches out of carbon fiber and painted them black with high temp flat black paint.
Search the archive for my write up a while back. All the details are there.
I have no marks on my dust cover any more and there have been several instances where that would have happened since if I had not installed the carbon fiber patches...
Best
Randy Snarr
N694RS
"Flight by machines heavier than air is
unpractical and insignificant, if not utterly impossible"
-Simon Newcomb, 1902
From: Steve Colwell <mcmess1919@yahoo.com>
To: lml@lancaironline.net
Sent: Monday, January 23, 2012 5:50 AM
Subject: [LML] Glareshield Fabric Melt Test- Update
Clark,
A better test for materials would be a magnifying glass. The tilt up canopy’s act just like one when the sun is behind them at the wrong angle.
You might try Flat Black VHT rattle can paint (for auto headers) on a scrap of fiberglass. If that works, you could test plot the area that gets the hot spots (in a Legacy it is the forward half of the dust cover).
Then stop the fabric before it gets to the hot spot area.
We are using Ultrasuede and don’t have a burn spot yet but it is fading to dark grey even though we are very careful to cover it anytime we are not flying.
A fabric that might work is thin Microfleece. Black is non-glare and it is stretchy and cheap enough to replace easily. Test it for flammability!
Steve Colwell