Slight lift out of case to graphic cards help please

[Jriker1]

I have a few cards in a computer case, top open. Want to lift the cards slightly higher to try and allow better cooling.  Plus adding a third card so need to offset them from the pcie slots so they aren't butted up. Of course need a riser on the cards. Thinking of raising them up a couple inches. Not sure how. Thinking of something to lift the cards up slightly on the backplane and get longer screws to screw them in. The backs of the cards would then hover over the motherboard slightly. Enough to clear the bottom of the risers. Any thoughts on physically what I could use to accomplish this or other ideas. Note looking for low profile ideas so no milk crates 😄

Thanks.

JR