You are right. The white letters look better. And the colors look great.
What if: Rockets Across America was a little smaller so it fits straight across the middle in 1 line ?
OR ... here are some other ideas.
What if: Rockets Across America was placed under Triumph and the extended stripes put back to like on the t shirt photo ?
Then it would be a little lower so the cross bar would not be as wide.
Then put Spearfish, South Dakota in the cross bar.
Then insert the four heads under the Brit +X design
Then RAA XI July 2016 under the four heads
Then 2300 CC at the bottom.
Just some ideas.