There is an FM App I am helping my Brother with that takes up all the screen real estate on the current iPad Pro (the Big One). I have tried to display this on the 12" MacBook8,1 and am unable to get it to work without scrolling the windows - not a good thing, but I have not been able to get him to re-size it to fit 12" and up - at least not yet.
There is a feature in FM to adjust the size by 25%. i.e., 100%, +/- 25%. It is in 25% increments. At 75%, I can see the entire window of the application, but it is too small to work with very well. If FM could somehow implement +/- 10% increments, this would open up a lot more apps for the 12" MacBook8,1. 90% would probably work for me and I could use most of the screen real estate on the MacBook.
Ultimately, I think redesign for 12" screens and lower resolution products is the answer - but the "designer" wants to make it available on an iPad Pro more than a 12" MacBook8,1. He designs on a 15" MacBook Pro.
In the meantime, I hope FM would implement +/- 10 Enlargement or Reduction of the FM Windows. +/- 25% is not where it should be. Too be fair, I know when FM could not do many things that it can easily do now; so, the have made great progress from the initial versions when a .pdf was not even possible, etc.
This App Does Not require Retina Display - most do not. It would be beneficial to keep the older machines (Macs & PC's) where they could use the new Apps.