Not necessarily true, I managed to get my Defi's in there and it looks OK - not perfect, but most people don't notice that they're not perfectly spaced out.
I would have gone with the Defi DIN cluster, but you can't specify which meters will go in there, so I went with separates so I could choose to my needs.
I got an off-cut of Poly-Ethylene from a plastics mob here in Sydney, and it cost me nothing, luckily! My old man and I measured and trimmed it down, and got a hole-saw to cut the holes, which took quite a bit of time. Another problem is that it's impossible to find a 52mm hole-saw, so like Hugh mentions, you have to file or burr the holes out until the gauges fit. Keep the holes a bit tight too, that way they won't budge while you're driving, and will be much harder to steal if anyone should ever attempt it. I made some small brackets for the back to secure the gauges to as well, just as added protection.