Back to school vest help

I’m making the back to school vest from [I]Fitted Knits[/I]. Unfortunately to get the same amount of ease on the top and bottom I need to make the next biggest size on the bottom (ribbing), and about 4 sizes smaller for the top. WTH?! My question is the best way to combine the 2 sizes. I was thinking about evenly decreasing just before I start the top part, or maybe gradually decreasing along the sides. What would be best?

I think the evenly decreasing might work better; however, I am not familiar with the pattern, so take my opinion with a grain of salt.