Here is how I was thinking when searching setups:
First, to be very effective, you should be able to link crMP after a meaty stHK.
Why crMP? Because stMP or stHP will whiff in some condition (crouched opponent, character specific, etc). I prefer always use crMP (which will ALWAYS hit), than try stMP and say “argh, shit, it doesnt work on him”, and lose the round.
Knowing that, you have to look at frame data.
When you hit with stHK at the first active frame, you are at +2. So, if you hit at the last active frame (8th), you will be +9.
CrMP has 7 startup frames. So, to do stHK -> crMP, your stHK has to be AT LEAST +7.
I dont like to play with just frame link. So, i prefer to have +9, and be confortable to do my link.
=> i have to hit with the last active frame of stHK
StHK has 8 startup frames, and 8 active frames. To hit with the last active frame, 15 frames must whiff (8+7).
Knowing that, and knowing how much time your opponent is down, you can find the setup you prefer.
For example:
Against most of the cast, EX oroshi knocks down for 68 frames (there are 5-6 exceptions (cammy, sagat, etc…)).
To hit with the last active frame of stHK (the 15th), you have to move during:
68 - 15 = 53 frames
(every additional frames will decrease your frame advantage)
Now, just find some move to fill 53 frames.
I use LP hayate (36) -> dash (17)
36+17 = 53
If you look at your setup:
stMK = 22frames
f+MK = 34 frames
22+34 = 56 frames
As I said, moving during 53 frames will make you hit with the last active frame of stHK, and you will be at +9.
Moving during 54 frames = +8
Moving during 56 frames = +6
So, with +6, you cannot link crMP (7frames).
And if you want to use character-specific/position-specific stMP or stHP, you have only 1 margin-error frame for stMP (5frames), and stHP is a just frame (6 frames).
The second thing I wanted to say about your setup, is that you use normal moves.
I hate using normal moves, because they cannot be buffed.
If i use your example (stMK -> f+MK)…ok, its 56 frames, ONLY if you hit the button as soon as makoto can move. Special moves can be buffed and then can go out at the first available frame very easily. With normal move, you can miss the timing and do it 2 frames too late (except if you p-link every normal move you use…).
If you do stMK 2 frames too late after your EX oroshi, and you do f+MK 2 frames too late after your stMK, you’re finishing at 60 (56+2+2) frames, screwing completly your meaty stHK.
Concerning my setup after backthrow. Yes, it can miss, because HP-hayate = 44 frames. And i need to move during 45 frames to use meaty stHK…so, i have 1 margin-error-frame.
I still didnt find a special/dash move setup during 45 frames after a backthrow (as i said, i wont use a setup with normal moves^^)