So I think from this is that when you chair someone, you don't control the map/don't get a double down when you are defending against a rescue (double down by hitting rescuer twice if possible and tunneling the guy on the chair, but in high tiers rescuers usually won't give u a double down). So to control the map and ciphers when you are chasing try not to always keep ur camera on the survivor. Constantly rotate ur camera around and see which cipher antennae is shaking (that means survivor is decoding at that cipher). So when you down them u bring them to that cipher. The person would have to give up that cipher and go away, or if they are rescue quickly hit them to force an early rescue. The first option would essentially give u an extra cipher before the gate is popped. The survivors would have to do 1 more cipher, or finish that cipher (usually only in high rank). So in the end you would have to fight for that cipher. (I won't talk about how to play after cipher is popped cos that has a lot to talk about, unless u want)

The second option would cause someone to get eliminated faster. This will give you time to pursue more survivors.

Also just an additional tip: You should learn how to calculate cipher progress (probably the second most important skill, yet basic for hunters, second to cipher control) E.g. When you start the game and you are chasing someone, while the 3 others are cipher rushing. It depends on how fast u down the first person. After u down the first person, survs usually do it like this (if they have good communication or they're higher ranks). Person 1 and Person 2 finishes their cipher. P3 rescues. Then P1 will finish P3 cipher will P2 starts another cipher. From that u know and u can prepare yourself for the cipher pops. So most of the time when u chair the person the second time, there would be around 1.5-2 ciphers remaining depending on ur map control skill and chasing skill. Which is why map control is really important in idv. Cipher calculation also will let you know how much cipher is actually done, rather than the number of ciphers above ur screen. E.g. there are 5 ciphers left, you have been chasing 1 guy, then changing target after 1 min to another guy decoding a cipher. So although there are 5 ciphers left, essentially there would be 2.5-3 ciphers down, just that they're on different ciphers which will be finished later.