I have often thought long and hard about growing different plants upside down.
A VFT, admittedly is probably one of the worst candidates for the experiment because they do appreciate especially strong sun, and their growth is not even remotely vertical.
However, I have thought of different methods for growing plants upside down, and although they are indeed completely unnatural, so is owning a Nepenthes in North America, so oh well, that's a totally bogus argument. Anyway, I've made a quick diagram to depict how I theorize upside down growing would be best accomplished. This is a cross-section of a pot for reference.
The plant would have to be entirely lighted by artificial means so that it isn't going against gravity by reaching for the Sun. Note how the inverse "slack potting" would essentially allow both the roots and the growth to use gravity to aid their downward growth.
The only added benefit that I would imagine would occur from growing any plant upside down would be that it would grow much faster downwards, although it would be weak, due to growing with gravity instead of against gravity. IDK, though.