Curved or straight Spring Bars when using Nato Straps?!

Hello

Recently i purchased the Nylon Fabric-Leather Nato Strap For My Apollo 8 MK2. Originally it comes with straight spring bar along with Rubber Strap.
When installing the Nato, it feels tight which rubs on the spring Bar due to the area between the lug and straight spring bar which is narrow.

My Q is:

1- Will this Damage the Strap if i keep using the straight Spring Bar?
2- Is it Necessary to have the Curve spring bar to make the insertion easy ( but it will take me more than 6 weeks to receive it after placing the order )

Thanks