I have measured the Sunny top to give you some more information. There is already a comment on Patternreview about the sleeves being too tight there.
In a size 10 the sleeves at the bicep measure 10". Same as the Pia. My actual bent arm at the bicep is 12". Now in a light stretchy knit this would still be OK but your fabric would still have to have at least 75% stretch I figure - exactly like the swatch in fact.
Many T shirt knits, particularly those with cotton don't have this.
I really like the shape of the Sunny but when I have more time than I have tonight I will be adding at least a couple of inches to that sleeve. Maybe that will ruin the design but I know from today's experience that I am just not going to be comfortable in a tight sleeve.
I would be interested to hear more about other experiences.
I am hot on the trail of a few TNT knit tops, at least one that can be tunic length with high day-to-day wearability.