Indica's true indica's do not tend to need a scrog for support, maybe 1 main stake but that is about it.
Chem/OG Lines are not Indica!! They are hybrid some nearly 75% sativa!!! You can see it in the stretch that is for sure!!!! There was also more then 1 article in both skunk and high times in regards to that common misconception.
Now there must be more going on that if you flip a 10-12in. clone it ends up 4ft by the end of flower. MY first guess is that your light is much 2 high, forcing the plant to stretch alot more then nessecary to get into the "Sweet spot" light area.
Second, to much P and K at the begining of flower will cause stretch as well.
I use bushmaster to limit stretch specially on anything from the Chem Line which is known to look like Bamboo from how bad it can stretch out. Also I run a MH or FLORO's for the first 10-14 days of flower in order to help keep node spacing tighter.
Other then that my 10-12in clone send up about 2ish maybe 2.5 ft tops and that is on the most sativy, lumbery growing stuff. Generally they tend to double if I dont bushmaster them..... It all depends on genetics but most of my SOG genetics I can top and then flip @ 10ish inches, they finish around 20-24in and have 2 nice 7-10in main colas per 92.6oz. sq pot.