What is the best way to mount these to a drywall ceiling? I don't want to use adhesive if at all possible. Is nailing to 16" joist spacing sufficien

In the answer provided, what does "Only run #2352 perpendicular to the wall." mean? On a ceiling only two of the four walls can be perpendicular.

General Guidelines • None of these products are to be used in load bearing applications. • Extra framing may need to be added to support material beyond span limitations. 2X (1 1/2” thick) wood is recommend for the additional framing. • If a seam is necessary within a 12’ run, a shiplap is preferred to help conceal any shrinkage. • Do not seam two panels directly to each other over 12’. Runs longer than 12’ must either be full pieces (up to 16’) or an expansion joint (rabbit or T-Mould) be used to allow for the expansion and contraction of the planking through temperature changes (pgs. 23, 24). • Venting must be added to soffits where applicable. Check with local building codes for requirements. #2352 3/8” Beaded Planking • Span no more than 12” between fasteners. • #2352 must also be glued to the framing/substrate. • Only run #2352 perpendicular to the wall.