A close call with a weak overhang years ago caused me to install 2 gable trusses at each end of a house, with the added benefit of better securement to the roof. A small amount of extra cost, but worth it, I feel.

While searching what would be a good product to use between the wood top plate and the ICF wall, I believe foam sill sealer works the best. The concrete will not be 100% smooth at the top of the ICF wall and the wood top plate will shrink over time, this will eventually lead to a gap between the two surfaces.

A foam sill sealer/capillary break is cheap insurance ($5 for a 50' roll) and will help with air infiltration and moisture migration.

   


They even make ones that are 7.5" in width:

Green Guard sill sealer