Hi Richard, 

have not used Western Hemlock but have used a number of other species.

if the wood does not have a clear reputation, you can always create a test piece (take a sample piece of wood and epoxy coat it)  and see if there is any obvious problems (e.g., the epoxy won't cure, clouds, or otherwise misbehaves. ) 

you are clearly minimizing risk if its only being used as an accent strip and the rest of the boat is something like cedar. 

i did look up its properties on one of the technical sites and there was no obvious problems.  you will want to make sure any wood like this that you are experimenting with is dryed and not just sawn from a raw log.

all that said, it did not strike me as having a remarkable color as an accent stripe and seemed to be pretty much the same visual effect you could get with yellow cedar which is well known in the boat building community and relatively easy to source.  it is relatively dense compared to cedar so you would not want to do more than an accent strip or you would have a pretty heavy boat.

anyway, i don't think you will have a problem but i would do the recomemnded test if nobody can vouch for it.  can you share what attracts you to western hemlock?

i have some experience with accent stripes (see pic below..this is a white cedar accent) so interested in what you are trying to do.

best, h

   apologies, boat above accent stripe is yellow cedar.

   Thanks for the advice , very helpful , I'm building a petrel