I'm only 135 lbs at the moment. I'm working on that. I tried the 45 degree variation of skull crushers with an empty Olympic bar and failed miserably. Should I buy a ez curl bar for these?

I'm running this program: https://www.muscleandstrength.com/workouts/jason-blaha-ice-cream-fitness-5x5-novice-workout
I only have a power rack so I replaced tricep extensions with skull crushers and hyperextensions with good mornings which feel weird as fuck, maybe a flexibility issue.