I have discovered that not only do Shared Events have to be done at SPECIFICALLY the sizes listed, locking you out of most of them if you prioritize the girls you like first, but you can't actually use saves to go back and see them later. I don't know if it's a bug or not, but certain flags are permanent and carry across saves. I tested to see if girls can be larger by getting Iris up to Stage 5, then Lucy up to Stage 2, saw that the event popped, and then got Lucy to Stage 3 to see if I could still do the event. I couldn't. However, when I went back to the save right before the event, with both girls active in the cafe with exclamation marks, Lucy suddenly disappeared off my screen and the event was entirely inactive - as the game recognized that Lucy had been bumped up to Stage 3. Definitely the worst of both worlds situation here.