You do not need to pull every carpet tight as a drum, and I can prove it
Everyone in this trade keeps saying you have to power stretch every single room, but last month I did a 12 by 15 bedroom in Abilene and left a little give in it on purpose. The homeowner called two weeks later to say it felt softer under her feet than the last carpet she had put in, and she wanted to know what I did different. I have been installing for 14 years and I have seen more callbacks from overstretched carpet pulling off the tack strip at the seams than from anything else. A carpet that is too tight ripples at the edges and pops loose when the humidity changes. Has anyone else tried leaving a bit of slack in a low traffic room and had it hold up?