I have tried both ways and was lead to believe that cutting the stems was the "correct" way, but before this had always cut at a node for the roots to grow from there. My results showed that cutting at the node produced roots faster, but cutting at the stem made less, but thicker roots. I have since decided to go back to cutting at the nodes as I would rather have roots sooner, instead of less, but thicker roots that take longer to form -- 14-21 days versus, like you, 7-10 days, when cutting at the node. I use Rockwool cubes with 99.9% success and use Clonex purple. I also scrape the stems lightly before placing them in the gel.
Hope this helps,.....
Organoman.