How to detail missile pod from Balden arms

Hello guys! Since I started modification and customization using Balden Arms, I kinda notice the Missile pod that was included in the pack. Initial reaction it was lame with out the front cover. 

Then it hit me like a raging truck. why not make physical missile heads into those holes to it would look more awesome. It got me thinking how to do this.

Then one day, I realized that the runners (from any kit) mostly have the same diameter as the wholes inside the missile pods. What's better is that runners (i have a stock pile of it) come in different colors.