A front-end attachment would generally be an “addition” within the meaning of 1910.178(a)(4) that affects capacity and safe operation. Section 1910.178(a)(5) assumes that the truck with the attachments will already be, “marked to identify the attachments and show the approximate weight of the truck and attachment combination at maximum elevation with load laterally centered.” However, before a non-factory-installed attachment may be used, the employer must comply both with (a)(4), by obtaining the truck manufacturer’s written approval, and with (a)(5), by having the truck appropriately marked.