I’ve been doing some research on this and here are the guidelines I was looking for. Just in case someone else comes across this thread with the same question. Having said that the advice I got here,“make notes of what you do and learn from experience” is the next step from this starting point, I am sure.
These are my notes from “Sous Vide Cooking a Review” By Douglas Baldwin.
Available here: Sous vide cooking: A review - ScienceDirect
Red meat:
At sous vide cooking temperatures between 55C and 60 C, many of the enzymes have been denatured but some of the collagens are active and can significantly increase tenderness after about 6 hours (Tornberg, 2005)
Collagen fibres start shrinking around 60 C but contract more intensely 65C Shrinking mostly destroys this triple-stranded helix structure, transforming it into random coils that are soluble in water and are called gelatin.
Muscles used for pulling the legs backwards have a higher level of elastin which does not break down with temperature. So toughness will not reduce with cooking.
In general, the tenderness of meat increases from 50C to 65C/ but then decreases up to 80C (Powell et al., 2000; Tornberg, 2005).
At 80C/176F, Davey et al. (1976) found that these effects occur within about 12–24 hours with tenderness increasing only slightly when cooked for 50 to 100 hours.
At lower temperatures (50C/120F to 65C/150F), Bouton and Harris (1981) found that tough cuts of beef (from animals 0–4 years old) were the most tender when cooked to between 55C/131F and 60C/140F. Cooking the beef for 24 hours at these temperatures significantly increased its tenderness (with shear forces decreasing 26%–72% compared to 1 hour of cooking). This tenderizing is caused by weakening of connective tissue and proteolytic enzymes decreasing myofibrillar tensile strength. Indeed, collagen begins to dissolve into gelatin above about 55F/131F. Moreover, the sarcoplasmic protein enzyme collagenase remains active below 60C/ 140F and can significantly tenderize the meat if held for more than 6 hours (Tornberg, 2005)
For example, tough cuts of meat, like beef chuck and pork shoulder, take 10–12 hours at 80C/175F or 1–2 days at 55–60C/130–140F to become fork-tender.
Intermediate cuts of meat, like beef sirloin, only needs 6–8 hours at 55–60C/130–
140F to become fork-tender because the tenderization from the enzyme collagenase
is sufficient.
I also found Purdy Pictures: The Charts to be helpful.
I hope it is of use to someone.
Cheers