MM, it has been over 20 years since I started playing this game, and I still fear Sinistar. The only hints I can impart to you is get those sinibombs as soon as possible, destroy those doggone tanks so they don't cheap shot you, and then get to a clutter-free area. Watch your radar, and as soon as Sinistar is about to come onto your screen and kick your butt, fly directly away from him and release those sinibombs. Sinistar tends to beeline right towards you, so unless there are obstructions, he should fly straight into the sinibombs. Just pray you have enough of them to kill him before he reaches you or one of those doggone tanks shoots you.