So I got my Slimline rack installed today. I can't upload photos for some reason, so imagine a white Rubicon with a Slimline rack in a piney forest.
The install went well. I really took my time when it came to drilling holes in the roof. As dstock mentioned, I needed to drill 16 22mm (7/8"ish) holes in my roof. That was pretty nerve-racking, and I definitely rewarded myself with a beer afterwards. Each hole is surrounded by a dense foam ring to keep water out. I'm thinking about putting a bead of silicon around each ring after it's had a chance to settle a bit. The roof is pretty hard, and can wear down a hole saw pretty quickly. By the fourth hole, it was smoking quite a bit and there wasn't much teeth left. From then on I coated the saw with chain oil frequently. That helped quite a bit. I still went through 4 saws for 16 holes, but they probably could have gone further. I wasn't about to cheap out though. I went for a cruise down some back roads, then drove 2 hours on the highway to my work apartment. The rack is looking a little crooked, so I'm going to readjust it when I get a chance. The instructions recommend taking it out and re-tightening the bolts.
I'm going to return the Spare Wheel Steps. It's a neat idea and it certainly looks well built, but it doesn't seem as useful as I had imagined. By the time you get to the first rung you're standing on the bumper and are high enough to deal with whatever is on the roof anyway. I'd rather just a get a plastic folding step-ladder.
Thank you again, Everybody, for all of your input.