[CApainter]

Have you considered Sika 1A polyurethane joint sealant? The thing with polyurethanes verses most TO2 acrylic/silicone caulking materials, is that the polyurethane is moisture cured and allows a full cure through a large bead of sealant. Where as, regular caulk has limitations on the gap it can fill.

In other words (per RH's suggestion) regular caulking will stay more softer and mushy rather than tight and stretchy if it is used on really wide cracks.

 

[CApainter]

The LP Smart Siding Installation Instructions specifies a sealant that meets the ASTM C920 Standards. Quad MAX OSI meets this standard but Quad OSI doesn't according to a bulletin submitted by Nichiha Fiber Board Siding.

It appears the sealants that meet the ASTM C920 standards can be single or two component, considered elastomeric, compatible with polyethylene(no transfer), and can be applied in cold, and I believe, to wet surfaces. As I understand it, this does not include silicone caulks.

Also, primers for LP SS should not contain vinyl, like PVA sealer, or transparent sta.