I stumbled across this thread late so I've had to catch up, but this topic is of high interest to me. I'm a hydro grower in a legal state and I've been on the hunt for THCV for a couple years. It's been frustrating. I've grown out Durban Poison from Dutch Passion, but it it appears it's been so heavily worked for THC that there's not much THCV left. I have a jar of fem seeds to share if anyone is interested.
I also grew out a Malawi (Ace) last spring, but was somewhat disappointed. It was a beast of a plant, but little 'V' as far as I can tell. I'm currently focused on Wild Thai (WoS) which is one of the few strains that mentions THCV in it's description. I've grown out 2 fems and they both definitely deliver a speedy buzz, but still not the level I'm looking for. Currently in the process of producing fems of the Thai.
There was discussion early in the thread re: THCV production being dependent on genetics or environment. I can say unequivocally that there is a strong genetic factor. Environment may regulate production through epigenetics or operon binding, but cells can't just think up a new metabolic pathway. You need the genes.
I'm happy to share experience and/or genetics related to THCV. Let's keep this thread alive!