Hi Wayne
I would leave the dew shield on, not because it's necessary to match your lights, but anything to keep extra light out is good
You want even illumination. But to be honest, this is one of the things you can do with or without. An even, white field is what you're after.
For the second question, yes that's great. I recently made something to hold something almost identical (ordered from Amazon, not Officeworks) for my refractor.
Here are some images, and with it being used last night.