Gable end trim work - pic attached

Evening all,
I hope this is in the right section.
I am about 90% complete on my workshop build, having done all the cladding and stucco work. I have a question in regards to the gable end trim work and the method of attachment.

On both gable ends, I have clad above the wall plate with James hardie 7.5mm FC Stucco. As is the normal in my area, I will then put some gloss white timber over the joins to create a nice federation look. What is the normal method of fastening the trim (16mm thick timber) to the stucco ?

In my head I'm thinking, use 40mm brad nails and a construction adhesive. the nails will go through the trim, stucco and in to the gable end truss. They will essentially hold the timber in place until the adhesive dries. My only concern is the nails / nail gun splitting the fibre cement, as ill be nailing relatively close to the edge of the fibre cement sheets.

Any tips appreciated.

Alex