It's not about the outer plates being thicker or thinner. It's the width of the inner block ---- 2 plates & rollers ---- that drives the bus here.

Connectors vary in terms of the usable length of their pins to match the inner links that they fit.

As Kontact noted, many chains are marketed as 6s/7s/8s meaning they're narrow enough for 7s & 8s and will also we work for 6s which is wider.

So, you need one says 6s, or 5s/6s. Better yet, measure the outside of the inner link, and buy based on that.