Use a PVA wood glue. There is also a water resistant marine variety avalible on all your butt joins. Try to use stainless screws if possible. I've seen drywall screws rusted up in walls that don't get wet. You can also get a outdoor carpet glue that only needs to be applied to one surface not both like contact adhesive. Silicon is more plyable than liquid nails which gets brittle over time and silicon also has better water resistance. Sikaflex is much better than silicon or liquid nails but costs more, it will also bond your ali angle to the timber much better. Good luck. I also need to find time to build my sub box for my Sanger. One day soon I hope
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