Need some help with sizing here:
How high to the faucets?
How deep should it be to not kink beer lines coming in to shanks?
How much space should I allow between faucets?
I set mine 13" from the faucet tip to the drip tray. The reason for that was to provide good clearance for filling growlers. My kegerator did not have that kind of clearance, so I was never able to fill a growler using it.
Your depth will also depend on what tubing you use. I went with Ultra Barrier Silver (good, but expensive). It's almost like silicone, very flexible and not prone to kinking. I still had to shave a bit of insulation out to allow them to bend though, so depth is definitely an important consideration. Remember to account for your tailpiece or whatever you use on your shanks as well. They also make a 90-degree tailpiece; the ones I saw are a little longer than normal tailpieces, but they'll get your lines pointed straight down, so no kinking worries!
As the others have said, 3" spacing is standard and I definitely wouldn't do less. I used a 20" tile for the backsplash on my tower, so my spacing worked out to 3.5". Depending on your build, your drip tray could impact your spacing as well. You don't want to set them too wide and find out your outside faucets sit right on the edge of your tray.
If you have your various parts on hand - tubing, shanks, tailpieces, drip tray, etc., I'd dry fit everything before you build to make sure everything fits the way you want. I probably spent as much time on my tower as I did the rest of the build.
