Ok guys

So, suspension per se does not determine the benefit of a dust cover, based on noromance’s testimony. I’m not keeping track any more, but I think there are 3 who use a cover while playing LPs. The rest of us are on the other side of the fence. If I had to put it in a nutshell, I would say that the use of a dust cover sounded closed in to me, just as no romance says. By now I guess we could collectively advise the OP to simply try it for himself and make his own judgment. By the way this has everything to do with sound quality and nothing to do with dust protection.

I take it off while playing. Simply because the hinges broke a couple of decades ago so it is either on/covered or completely removed. I do not put it back on while playing not to accidentally make some damage while positioning. It comes close to the weight, etc.

Technics SL-1200G and SL-1600MK2 both dust cover down

The manual of the VPI HW-19 MKIII recommends that "the dust cover be down when playing records. Under most circumstances this will result in cleaner sound since the cover acts as a 'shield' against acoustic feedback." And of course keep the record and stylus clean. 

Put. me in the cover on camp. SQ better.