Hey! 
It's been a hectic few weeks (aside from the holiday, found out that my baby niece will need brain surgery coming up this month...
The rack is finished and now has the large cage sitting on top of it (which helps keep in heat).
While I was getting ready to move the large cage into the room (found out it wouldn't fit through the wee tiny doorway so we had to modify the cage before we could get it in), I put my two surinams into the rack (one in each tub). Bear in mind that this rack was not built with keeping a heavy female adult surinam in it, I pretty much had to do this temporarily until we figured out how to modify her cage. What I noticed was that with the large (8.5') heavy female in the top tub, with the drawer pulled all the way out, the front of the drawer dipped or sagged down a few inches. The female is extremely heavy (I can barely lift her on my own). The drawer slides didn't break, it just tipped downward when fully extended. Even partially pushed in, it levelled out just fine (nothing bent).
The female is now back in her wooden cage, which is sitting on top of the rack.
With the male surinam in the bottom drawer, with it pulled completely out, it doesn't do anything. He's 7.5' long and much lighter-bodied. So this design would seem to be great for adult males that aren't obese or overly large, juvenile females or smaller varieties like hog islands and nicaraguans.
So, if you were to make a drawer-rack like this, don't plan on keeping large BCI/BCC females in it (though, again, I never planned to use it that way, it will house adult males only). Well, you could, but you might want to make a prop or leg of some kind to help hold the outer edge of the drawer up when it's completely opened. That, or use more heavy duty drawer slides than I did (mine were rated for 75lbs, they make them rated for 100lbs and 150lbs). I saw on another site someone used drawer slides meant for tool chests which telescoped instead of just overlapped, and they looked like they'd work great, though I don't know how much they cost.
Other modifications I did.....
I put flexwatt on the bottom of each tub and put Reflectix underneath (to reflect heat upward into the tub). This is duct-taped into place. The upper drawer has a thermostat probe resting between the flexwatt and the tub. After monitoring that for a day, before the snakes went in them, I wasn't happy with the temperatures, so I went ahead and took the rest of the flexwatt and closed off the open space on either side of the rack, and on the back of the rack. That worked well and the tubs got up to temp (each tub has 2 feet of 11" flexwatt).
I also stapled an old curtain on the top rail of the rack, so that it would hang down over the front of 1/2 of each tub to provide a little more privacy since neither tub has a hide.
I will take photos tonight, sorry for the long delay, life interrupts.... heh.
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Lauren Madar - OphidiaGems.com
1.0 Ball Python, 1.1 Hog Island Boas, 1.1 Hypo BCI, 1.1 Surinam BCC, 0.1 Green Tree Python