Carpet is made in rows running the length with an empty space between the rows. If a carpet is going to wrinkle, where do you think it will wrinkle? The path of least resistance, I would think, between the rows. Like a piece of seam tape, which way does it bend easier, with the rows or across them? As for the stretching, I am a firm believer in power stretching. My rule of thumb of how large a room should be to use a power stretcher is that if it is bigger than a phone booth, power stretch it. I never said don't stretch the width. I said do the majority of your stretch in the length on angles. The length is where carpet stretches the most; the width is where you will get the least stretch. The techniques I outlined in that article are techniques that work for me. I don't have re-stretch problems.
For the mills to suggest all carpets should be stretched 1.44 to 2.16 inches in the width is ludicrous. Power stretch as I suggest in that column, use these new sealing tips for hot glue guns and your seam peaking problems will be significantly reduced and without the worry of future re-stretches.