Counter sink bits and bolts?

I am wanting to cover bunks on my trailer with 1/2" poly strips. I'm not so much of a do it your selfer, but I think I can do this one. I would like to know about counter sink drill bits and whether screws or through bolts would be the best way to secure the Poly Planks to the bunks.



Please let me know exact bolt/screw sizes with corresponding bit sizes you all would suggest. The bunks are 2x4 on flat sides not edges. I think I'd prefer to through bolt unless the consensus here says otherwise.



Thanks for your suggestions. Hope this is the right place to get expert advise for this.