When can you start topping your plants? ...
bla-bla-bla
To me, it always about the roots !
I do a lot of topping, fim'ing etc to my plants....
I have topped at 17 days old in a red solo cup... to two nodes... I think 17 days is early unless you have a thriving clone/plant I top, and grow my own clones-horehound...
That plant [vegged in veg room to 14.5"...my max height] once put into Bud at 8 weeks of veg, grew to be 28" tall with two beautiful spears, and colas....
Roots are the most important thing.... Only FIM/Top/Transplant when your roots are good/great....
Oh yea, on that 17 day old plant, it's clone also grew out right after the first topped at 17 days... I transplanted the top [cloned it], and it also grew out perfectly....it went into the bud room 4 weeks after it's mother...
Good Luck man...