In a thread, titled Zangief 2012. Many posters were wondering about the use of the far st.hp knockdown, with not much materializing. Sorry its taken me this long, as I’ve only recently updated to the 2012 version. Very slow I know. 
Here’s a refresher course for the move’s frame data: in my own notation; start-up, active, recovery, on block, on hit, damage, stun
Far st.hp [12-3-18:-3/d]=140(200)
It has slow startup - but most importantly, its hit box arcs downwards, so doesn’t give it any anti-air utility - however will hit crouching opponents I believe. The only way to set it up, is to precede it with far st.lp (most frame advantage move) on hit. Frame data says the st.jab is +6 on hit (Maybe +7 in the 2012 update).
Think of the use of the far st.hp, as though it were a reset or alternative to tick SPD. Ideally, designed to tag an opponent that has “pre-committed”, to a defensive option - especially jump back and neutral jump, with a chance to tag back dashes. Although, highly dependent on back dash quality - thus match-up dependent. Fortunately, Sagat’s back dash is theoretically vulnerable. Just like tick SPD, you lose to reversal. But there are benefits, in scenarios, where regular GH or EXGH is blocked, when you incorrectly guess back dash, and your EXGH or GH loses to jump back attack. Far st.hp is relatively safe on block -3 (possible caution - shoryukens), and you are well spaced to not be hit by 3 frame moves - throws, jabs and shorts.
A mention about the “theory of pre- commitment”. When you are in proximity and at advantage frames, your opponent has to guess against the threat of SPD. Reversals carry their own risk. And I’m willing to gamble, on the fact, that they are not waiting around, to react to the slow startup of Zangief’s far st.hp. They would have already decided their course of action well before.
As previously mentioned, far st.lp on hit, is required for the reset. And can be set up in a few ways.
a) st.lp. st.lp. far st.lp - far st.hp (most easiest to do for me)
b) cr.lp. cr.lp. far st.lp - far st.hp (couldn’t get to work for me)
c) post SPD-LPGH (+3) - far st.lp - far st.hp
d) post EXGH (+1) - far st.lp - far st.hp
*Key Notes: Success depends on getting the nearest far st.hp, which relies on getting the nearest far st.lp. So make your chain cancels as quick as possible. b), c) and d) haven’t tried yet - only theoretical at this stage. But if your frame perfect, it should work.
For jumps, the mathematics to make the far st.hp tag work. +6 from the far st.lp on hit, then +4 for your opponents pre-jump frames. Subtract, the 12 frame far st.hp startup, means the 2 frame difference, makes it possible to tag jump backs, and neutral jumps early when they leave the ground and are within reach. If they get greedy, and go for neutral jump, its more easier. When you catch them in the air this way, follow up ONE hit EXGH is possible.
Tagging back dash, I haven’t been able to confirm as yet. But its limited to back dash quality, namely, duration and distance. Basically, after your far st.lp hits, and they immediately go into the 8 invincible back dash frames, your far st.hp should tag them right after. 12 startup frames - 6+ from lp + 3 active frames = 9 frames.You can hit them on the 9th frame when they are out of invincibility.
Could possibly be used during post SPD-LPGH by whiffing far st. lp when they back dash and immediately going into far st.hp. For a total of 26-3=23 frames till active. Not sure as yet, on its viability in post EXGH back dash scenarios, due to the further range.
Keep in mind I’ve only spent 2 hours working on this concept. So its still in its infancy. There’s 6 frames your opponent can use to react to the startup of your far st.hp. But you could easily opt to complete the combo, instead of going for a reset. eg. combo into far mp.
Time will tell whether it becomes viable, but once we get over the hurdles - proper spacing, timing and know more. The follows-up available from the soft knockdown, might allow you the luxury of a cross-up, where an EXGH combo won’t.
Thanks for reading.
If this fails, then I really don’t like the idea of this knockdown being added to the game, as a means to recklessly get in on Sagat’s far hk. Because you can, but its a reckless guess. Still might be better than reckless jumping.
Additional thought:
Used on its own. It could be a good move to catch some short back dashes. As noted, compared to gh its safe on block if you guess wrong. But if you face a reversal, your Russian bacon is just as cooked, as the other options - st.mp, cr.lk, st.hk or SPD.