I'm trying to hunt down some 6 inch VC filters, but have been offered the small 3.5 inch sheets. Is it ok to place them between the bottom condenser lens and the negative? Will that make all of the scratches on the filters visible because of the proximity? Or should they go above the first condenser lens? I don't want to save a couple of bucks and have artifacts in the prints. I am using the big D2 variable condenser.