They grow up so fast
Putting on the suit was the easy part, he wasn´t especially big, zipping it all the way up was harder. But he succeeded in the end. The mask was in place and he waited for the changes to happen.
It was like when you fill up a sumo suit with air, but instead of a big plastic wrestler you fill up a beutiful blonde girl. The excess parts of the arms, legs and body filled up. Tommy noticed how he suddenly was much taller with longer legs.
All of him felt bigger. Longer legs. Longer arms. Bigger butt. Squishy breasts. Longer hair. The list went on.