No matter how hard I have tried till now, there is something or the other always missed while writing the answers against guideline answer.
I am really starting to believe on the subject line 
For me, the one part that is clearly and without fail entirely subjective is the risk objective. I cannot for the life of me figure out when a portfolio is “large relative to expenses”, or when living costs are only moderate… etc.
I have seen NUMEROUS examples where the required return calculation exceeds 7% net nominally, yet they say in the risk section that expenses are small relative to the portfolio… 7% nominal is NOT easy to acheive, particularly considering that it is closer to 10.8% grossed up at 35!
Other than this I think most of the IPS is fairly cut and dry, but in the end it is all about reading very carefully and paying VERY close attention to timing of cash flows.
Whenever anyone tells you something is an “art rather than a science”, it means they don’t know wtf they are doing. IPS definitely falls under this category, since you can generally rationalize such a broad range of variables.
This means I still need to dive more deeply into it…argh
Reading the question VERY CAREFULLY is really a key…
When I took L3, I did poorly in IPS. However, so did everyone else. At some point, further study does not help. The answers for that section are subjective and poorly justified. You should try your best, but be prepared for the possibility that you will not do well in that section regardless of preparation. Your performance in the non-bullshit sections will determine your pass/fail. That was the case for me and for most other AF people. (You can look up the past score matrix thread).
I tend to agree with the sorrows expressed in this thread…i will just hammer down the framework/logic and be flexible when it comes to application…as best as i can…