I have one of those China knock-offs I from ASA. You adjust your elevation just like normal with your front sight post. I didn't mess with any aperture other than the big one and I only zeroed it for 100m on a steel plate. I guess I lucked out, because I really didn’t have to do anything other than bolt it on.
If you need to switch to your flip-up, things have gone way south for you anyhow and it will most likely be up-close work. I wouldn't trust a flip up for any long-range stuff. The Knight is nice, but expensive. I like the DPMS A2 sight (looks like a chopped carry handle), they work really sweet with a dot sight, like oh I don't know, the OKO for example ;-)
I have a guy down south who is going to give me a prototype of a flip-up he made. I'll let you know how it turns out.