I benched with chains for the first time. I bench raw. I put 20lbs of chain on each side connected by EZ straps I purchased from Elitefts. All the chain was deloaded at the bottom and off the ground completely at lockout and unracking it. Doing it this way though I was only able to press 5 lbs more at lockout than my most current straight weight max. And that was 40 lbs less at bottom. So 210 at bottom and 250 at lockout. When my most current single was 245. I keep reading of guys doing 100 % or more at top but it just seemed harder for me. Also could feel the stabilizers working harder with chains on side. Is this normal to be harder? Only 5 lbs more? I can definitely see how I’d benefit from accelerating more.
You tried a new movement for the very first time: it takes time to develop the skills to get good at the movement.
Chains add more than just weight, as mentioned. They add some dynamic instability to the bar and they force a more explosive concentric (or you’ll get stuck). I’d imagine you’ll improve quickly.