Exactly, but you guys are missing a bunch of considerations. Namely ergonomics.

The assumption is that your additional gauges are to compliment your existing ones, and that you'll be attempting to read everything while driving. In that case, you want your gauges to be the same distance from the driver's head so the driver doesn't have to refocus his eyes for every gauge. It also makes it easier to spot the other gauges in your peripheral vision. This is the idea behind mounting a single gauge on the dash hood about 6-8" back. It puts it about the same distance into the dash as the stock cluster.

The worst thing I've seen, function-wise, is the tripple a-pillar gauge. It puts the top gauge right next to your head, about 1/4 the distance as your cluster!

The less you're going to use a gauge, the farther away from the ideal it can be placed, uh ideally. Turbo timer, boost controller, fan controller in the console/dash, no problem. On top of the column, no biggie.

There's also the line of sight to consider. The farther away from your normal driving line of sight, the bigger a pain in the ass it's going to be to check the gauge. Yeah, the a-pillar might work great for all-left Nascar or right-hand drifts, but what about the other direction? They might as well be in your back seat! That's also my beef with boost gauges in the cigarette lighter hole. There's no way you can drive and stare down at 45* to read the gauge... ok, uh, there's no way that's safe, any ways.

Lastly, be honest here. Are you really going to read 45 gauges mid-drift/turn? Are you really worried about 45 different engine parameters failing on you mid-drift/turn? If you're really concerned about something, that gauge should have a warning tone/light. And if you're concerned about 45 things, consider building a more robust/reliable engine!