How to pin on race numbers—it's a topic I love, some for the rhetoric of the argument, but also because I think it demonstrates a person's perspective on bike racing and their ability and/or willingness to see it from different perspectives. So a little commentary on the topic....
(The following addresses the #1 technique for quality number pinning, but for a more instructional and comprehensive coverage of the topic, check out the original Race numbers: Pinning and Placement.)
Bike racers want their numbers to lay flat and not flap in the wind. They think that crumpling their number helps this. Let me give you the secret: 8 pins. Not 4 pins (and absolutely not 4 pins using the provided holes—this is cycling, not sailing club), not even 6. You get a handful of pins at nearly every race. Save a few. Then don't be lazy, don't whine, use 8 and this entire official/racer argument goes away, save the lazy bike racer.
But of course, bike racers are (by definition, I believe) lazy. So we have a problem.
For officials, seeing the numbers on riders whizzing by 5 deep at 25+ mph is an exercise in futility. A single line at 30 mph is no better, but this is the job of the official. Some officials are lazy, too (former racers?), and don't actually try to read all the numbers every lap, so they don't care how numbers are pinned. These officials should be stoned--they are the ones that take a millennium to figure out results because they have no practice at picking out 10 places in order at the finish. But most officials do care and spend the entirety of a race trying to decipher the perspective-bending Dali-esque attachments racers manage to make with their numbers. For them, crumpled numbers are the emblem of their nearly-futile task, not the cause of it. Sure, the stickler quotes the rule book, but one of the jobs of an official is educating riders. Aside from the occasional power trip, it's just part of the job.
So we have lazy bike racers and officials who've found a scapegoat for the nearly impossible task of reading thousands of numbers during a day.
The reality is that the rule is stupid for three reasons. First, like all other riders, I pin on my number, warm up, go to the bathroom, sit down, load and unload my rear pockets multiple times, and perform numerous other actions that WILL crumple my number whether or not I did it intentionally.
Second, the Tyvek material used for numbers reflects sunlight pretty well if you get the right angle. A poorly crumpled number (intentionally or incidentally) will probably have a few surfaces that reflect light and reduce the visibility of the number. However, a pristine number can reflect light across its entire surface rendering it completely illegible.
This illustrates the third point that proper placement of the number is usually far more important than the surface smoothness for visibility of the number. Up on the back: bad. Down along the side of the jersey: good. Right side up? Yeah, I'm talking to you, genius--put your number on right side up. (Cat. 2 - Cat. 5 -- I've seen them all do it this season.)
That all points to the fact that you need to learn how to put on a number like a pro. When you crumple the number, don't just wad it up and be done. You need to decimate it! You're not buying a new iPhone because it has 16 icons on a screen--you want it because the pixels are so densely packed you can't even see them! So get comfy and start crumpling. And rolling. And flexing. Now repeat. Finally, find a nice edge and smooth it all out. Hey, don't rip it--that's way amateur. But when you're done, the thing should feel like silk and lay on your jersey like your head on a 400 thread-count Egyptian cotton pillowcase.
Once you take the pro approach the officials won't notice a thing but the high resolution outline of your number. Unless it's upside down. Or on your back. Or flapping like a sail from 4 pins poked through the 4 dummy holes.
So just use 8 pins, put it on your side, and get the race started already.