I'm experiencing a lack of clarity on this.
Now, understanding 4th species in duple time is a matter of understanding Fux's text and seeing it in actual use. In 4/4 for example, it is easy to see the strong beat / weak beat relationships between beats 1 and 2 and also between beats 3 and 4. You can even see the strong/weak relationship between the first half and the last half of the measure, which is why it is justifiable to hold a suspension dissonance until beat 3 in 4/4.
I have also read that 4th species suspensions are a 3 beat action: a weak beat preparation, strong beat dissonance and finally weak beat resolution.
Yet, things aren't so cut and dry in triple time. Fux himself applies only a few paragraphs (if that) to the topic. Fux simply sees triple time as 2nd species with an extra beat. A dissonance can occur, for example, in the middle beat in 3/4 time with a stepwise bass. This makes sense and shows the relationship with 2nd species. With some observation of triple time, it seems to me that in triple time you can have a passing tone on beat 3 moving to consonance on beat 1 of the next measure using Fux's logic of the "2nd species extension." This also makes triple time interesting due to its variability.
Where it gets dicey is 4th species.
In the following please note that I am speaking strictly of a situation with 3 quarter notes in a bar in 3/4 time. I do understand that you can divide each of those beats by 2 and now you have created 3 smaller strong/weak relationships. This is not the type of action I'm referring to.
Now anyone can see that in 3/4 time, beat 1 is obviously the strongest beat. Therefore, a beat 3 preparation, beat 1 dissonance and beat 2 resolution seems very logical. But, if we take Fux's logic into consideration where he sees triple time as simply 2nd species with an extra beat, one would almost be inclined to believe that you can do a preparation on 2, dissonate on 3, and resolution on 1.
Yet, the aforementioned action goes against "prepare on weak, dissonate on strong, resolve on weak" literature (the final step in the aforementioned action actually resolves on a clearly strong beat.)
I'm working on a Scarlatti partimento right now in 3/4 time, and it seems to me that his approach to the problem is to prepare on 2, dissonate on 3, continue dissonance on 1, and finally resolve on beat 2 (ultimately a 4 beat action.)
Yet, I'm very interested in the experts take here. I thank you much in advance for an answer that will help me in my understanding of music.