With the FRP panels, they have trim/moulding pieces for the joints between the panels that allow some movement due to thermal expansion/contraction, so tape shouldn't be required. Also, some are manufactured in 4x12 panels, but not likely available at Lowes or Home Depot. With these larger panels installed with the long dimension vertical, you wouldn't have any horizontal seams. Also, rather than screws to attach the panels as I previously mentioned, there are FRP panel nylon rivets in which you drill a 1/4" hole through the panel and the plywood support, shoot in a little silicone to water seal the penetration, then drive in the nylon rivet to hold it in place. This also allows some movement of the panel due to thermal expansion.

The FRP panels are tough, but they do need a structural backing such as plywood. You might go by your local Lowes or Home Depot and check them out in person.

Excellent. Thanks for the info...!

craigtoo, would be glad to helo you source the right panel for your needs, sent you a PM

wood kiln was accomplished using 6" PermaTherm SIPs
2 men easily lift wall panels

Lots of good thoughts.