@lewm
I've just re-read the thread and as I thought, no-one said they had measured a difference in VTF. Two said there might be a difference.
So far then the score is nil posters have measured any difference. We've all got those digital scales, so why not get down to it - a minute or two's effort. I would certainly try, but I don't have a dust cover.
The subject is interesting because this is one pretty stupid tweak where a scientific measurement can easily be made, and proven by weighing with cover off and then doing it again to test the scale is true. I'm putting my money on 'no difference'.