I don't know about mid size truck frames but on big rigs, drilling any holes will automatically void warranty...I drilled one per side for Shrock sliders but 12 sounds sketchy...might be better to weld it on?
I am concerned that welding could affect the hardness of the frame also. It seems the frame is made of hard steel and that usually requires heat treating. Welding may only soften localized areas, but that is where the sliders are mounted. That would concern me.
