Great concept, great style. I wish there was a limit to how many items I could use. Nothing is stopping me from placing as many boosts as possible to get to the end quickly. Constraints bring creativity!
AH I see, I thought it was time due to the big timer and how the UI made a big deal out of the PR. In that case I would say what you have works well! Would just give the freedom to the player to place anything rather then picking from a random 3. Great work again!