I have gained 3/4 of an inch in the first 2 months of using a rod based extender, as tight as it would go. My thoughts are that hanging beats extending , this is pretty much accepted. Hanging utilizes high force.
The studies on extender use have shown that the majority of gains come in the first month then slow down.
Personally I was so excited about the gains I got with a Leluv slider extender I purchased a male edge thinking if the cheap junk rod based one worked that good an expensive one would be better. I logged another 240 hrs with it and got ZERO gains. This caused lack of motivation and I eventually quit. Since the stay at home order I am 118 hrs in with the slider and have gained a solid 3/16” . This is 3-4 hrs a day of as tight as I can stretch and always until I reach fatigue when I can’t take any more.