Very light tension isn't necessary. Medium to light tension is fine, the trick is to get it to "false set" it's when the cylinder turns a bit but not all the way. What's happening is the spool pin is catching. (it was the second pin going in on mine) I suggest that you rake the cylinder with a small diamond or just your favorite rake with medium tension. Once you get a false set, single pin pick (spp) by applying pressure to each pin one at a time, while having light tension. If you feel the cylinder trying to spin back (the tension wrench will push back) then lighten up the pressure just enough to where the pin will set and the cylinder goes back to the false set (this means that that pin isn't false set anymore and actually set). If the pin is fully pushed and the cylinder doesn't false set (or full set if it's the last one) then you'll have to release tension and hope that not all the pins reset, giving you the false set again.
So in short:
Rake with medium tension until a false set is achieved
Single Pin Pick (SPP) with light tension
If the cylinder doesn't re-false set when a pin is fully pushed, release
pressure and if necessary start over