Hey boris90,
I’m sorry to hear you got no gains from the extender. I’m back using one as I had some success using one many years ago - I gained about half an inch with just the extender. I’m wondering about how you wear the extender plus which line the tension gauge is at when you stretch. I would typically wear it after a shower so I was warmed up then only usually have it on the first gauge -1200gish. The extender was pushed hard into me from the start of me using it, bone pressed. I would alternate between down either leg, up and straight down for 2-3 hours everyday - like 20 minutes each then change. If started losing tension I would then increase the stretch or rods till I got to 1200g again. I don’t think I ever felt like I was going overboard or doing it too much as the tension was quite low but constant as I did it every day. I did have days were I could stretch but I didn’t worry too much and just carried on the next day.
I found wearing it like that meant I could do things around the house after work etc. This gained me 0.5inch in BPEL after 3ish months. I broke the extender and didn’t get another one as I was pretty happy with the result. My results were kinda in line with studies on Pubmed wear men wearing extenders gained around 1cm etc.