The light shroud is unlikely to do anything. That's not light coming from outside the scope but rather reflections around the optics from a bight star outside the FOV.
I have seen them on my CDK and been through the evolution process where Planewave bit by bit sorted them out.
What they did was:
1. Redesigned the secondary shroud so the section that extends out from the mirror was 4-5mm thick where it met the mirror and tapered out to 1mm thick at the end. This effectively covered the first 4-5mm of the secondary mirror and prevented some of this arc shaped reflections (hence the round shape of the reflections).
2. Provided several cut baffles, one around the primary where it meets the internal shroud, one on either side of the corrector lens. These were basically like a stiff cardboard disc about 15mm wide to stop bright edges of the corrector lens or edges of the lenses from causing reflections.
3. I flocked the trusses but it did nothing. I flocked the inside of the secondary shroud and the walls of the main tube and that seemed to improve contrast a bit. But it was 1 and 2 above that handled the reflection arcs not anything else.
A turned down mirror edge is also a common error on RC optics
See a fair way down the page here:
http://www.bbastrodesigns.com/JoyOfM...Polishing.html
The main mirror at the very edge really needs to be covered by a baffle. A 4 or 5mm wide black cardboard to cover that last 5mm of the mirror which may have a poor edge and also cause problems. My Planewave has a metal ring that covers the last few mm of the outer edge of the primary mirror. This would be important to check you have one and if not that should be done as well.
Greg.