(It seems every time I post it's about that elusive snake rack... I had to wait forever to scrape up the money, but I will hopefully be building it next month!)

When I'm screwing the shelves onto my XPVC rack, would you guys recommend I use spacers? I was thinking of a single CD on either end, just so I know it'll slide easy. Also, since the Vision tubs don't have air holes, I figure a small gap is needed for ventilation. Should I use something even thinner to prevent escapes?

Also, what's common rack substrate? I'm going to be housing a variety of snakes (see signature) and was planning on paper towel with a thin layer of aspen on top.

Thanks, guys! I'm very excited about my snake rack and just wanna hammer out the details.