I've been buying bi-metal blades for my bandsaw, and have been quite happy with them. Someday carbide will be available- for years you could only get carbide in a circular blade. Recently, carbide has become available on recip blades - boy, do they cut!
Your project is inspiring me to make an insert for my home shower - wife and I both feel the need. I should probably just buy some to get a feel for needed slat thickness and fastening - ie: ipe to ipe with epoxy.