isn't exactly a journal, but it helped me get a general idea when I started mine. Unfortunately sororities are very unique and what works for one might not necessarily work for another. My sorority is relatively young (months instead of years) but these are some things that have worked for me:
The only problem I've heard with under stocking with such a large tank, is that the girls sometimes forget the others are there and then have to re-establish territory over and over. I personally have 7 girls in a 13.5 gallon tank. Sororities aren't something you can just rely on the conventional stocking limits (according to AqAdvisor I could have 17 girls in my tank and be fully stocked), but the general consensus seems to be higher numbers of at least 5 seem to work the best.
I spent a lot of time at the store putting cups next to each other to evaluate the reactions and tried to pick the most non-reactive girls I could find. Also releasing them into the permanent tank at the same time is very important. It's too hard to judge the hierarchy beforehand and they'll surprise you even after all the time in QT.
I've seen sororities with tank-mates, my personal one has red cherry shrimp and nerite snails, but it depends on the personalities of your girls.
Generally you want the youngest girls you can find, and of similar size. I can't comment on the siblings thing, but I know for me having different colored girls makes it easier to monitor everyone.
I've found that mid-top level coverage is more important than lower, my girls seldom use the hides on the bottom.
I quarantined my girls in a partially filled cycled 10g. They stayed in their individual cups for the first two weeks, I rotated their position so everyone got used to being around everyone else. After the QT period I started releasing one girl into the 10g tank and letting her swim around the others so they could get used to more interaction. I cycled through the girls so everyone had a chance to be loose and swim around while the others were still in their cups. The longer the QT the better in my opinion, my way just involved a LOT of daily water changes.
I also use a more powerful filter on my sorority and the areas of fast current (not the entire tank) can help interrupt chases/aggression. It is also beneficial to have a tank that is longer rather than taller.
I'm not the best person to talk about dealing with aggression because I haven't had to separate anyone or deal with any injuries, but that link gives good ideas about "timeouts" and other things you can try if you encounter those sorts of problems.
Overall; remember that they aren't many rules that can guarantee a successful sorority, but once you find what works for you don't mess with it (no matter how tempting that new mustard koi female is