Solid rocket motors can be limited to a percentage of their maximum output while you're building the rocket! This really upped my game when I figured it out. I

Solid rocket motors can be limited to a percentage of their maximum output while you're building the rocket! This really upped my game when I figured it out. I try to plan my first solid booster stage to end before I need to extend the gravity turn into orbit, so I can shed the solid rocket booster mass and make the best use of my liquid booster delta-V, and additionally so the jettisoned solid boosters don't end up in orbit with me.