Hello, I used to do cliffhanges some time ago and now I would need some tries... I typically did them with a reverse bar position just because the distance to the bar is less which makes it easier when you go into the cliffhanger and also if you go out, even with zero offset forks.
How tall are you? Of course a shorte frame makes it a little easier to get behind the seat, but I tend to say you can learn any trick on any BMX bike, but of course a suitable geometry makes it easier.
If you are able to enter the position you may try to control your bike with your knees pushing against the frame from the sides. I feel this makes it more stable. The cliffhanger is a difficult trick and you need to be careful, especially because it is likely that you get caught in the bike somehow when you want to step/jump out of the trick when you loose the balance. But it is worth it! A nice looking trick and a very special feeling doing it compared to other rolling tricks!