I ran a session last night where our monk used his flurry of blows to incorporate a spin kick to deliver a stunning fist attack.
I let it happen, even if by name it made no sense.
Looking at the description for each part of the process, it seems that by RAW it looks like it stacks.
You must declare that you are using this feat before you make your attack roll (thus, a failed attack roll ruins the attempt). Stunning Fist forces a foe damaged by your unarmed attack to make a Fortitude saving throw (DC 10 + 1/2 your character level + your Wis modifier), in addition to dealing damage normally. A defender who fails this saving throw is stunned for 1 round (until just before your next turn). A stunned character drops everything held, can’t take actions, loses any Dexterity bonus to AC, and takes a –2 penalty to AC. You may attempt a stunning attack once per day for every four levels you have attained (but see Special), and no more than once per round. Constructs, oozes, plants, undead, incorporeal creatures, and creatures immune to critical hits cannot be stunned.
At 5th level, a monk can learn one type of style strike. Whenever he makes a flurry of blows, he can designate one of his unarmed strikes as a style strike. This attack is resolved as normal, but it has an additional effect depending on the type of strike chosen.
The monk spins about, delivering a kick his foe did not expect. The monk makes his attack against the foe's flat-footed AC. Creatures with the uncanny dodge class feature or a similar effect cannot be caught flat-footed by this style strike. The monk must attack with a kick to use this style strike.
So by RAW, stunning fist, while it implies that you are using a fist, does not actually require a "fist", but an unarmed strike. Unchained monk, (created after stunning fist) incorporates kicks and headbutts, and other flavorful attacks, however I do not think the creators ever intended a monk to use his legs to deliver special attacks.
Can someone advice on this situation?
I will surely be stunned by a well placed kick. You don't need to hit someone head to attain that effect. A kick to the testicles or other sensible part of our anatomy will stun most of us.
RAW, I don't see any reason why it shouldn't work.
See, And I am more inclined on letting that ruling to be, however what I am worried about is:
-He can use spin kick unlimited times a day, and once every flurry of blows.
-He can use flurry of blows unlimited times a day.
-And he can use Stunning fist 6 times a day (he is a level 5 monk)
So that is 6 times a day he can target flat footed AC (as opposed to normal AC) with a stunning attack.
pelvic thrust
Although that would drive them insane instead of stunning them!