I found a Simpson strong tie product (BC40Z) 4×4 half post base, and it states its intended use is for attaching a 4×4 railing post securely on top of wooden decking. The following picture demonstrates a proper installation.
I got excited about it and bought a whole bunch but then thought after the fact that I probably should have checked to see first if it is acceptable and code compliant to install to install securely on top of composite trex-like decking of about 5/4" nominal thickness.
I can't find any information, even information on the Strong Tie website that states NOT to install on composite decking. It would be so much less of a pain to use these. They are held down with a carriage bolt and 4 16D joist hanger nails, and they are attached to the post itself by 3 16D joist hanger nails on each side.
Best Answer
Railing post should have been a prerequisite thought in the process of building any deck. As far as attaching to Aztec or trex product decking it is not sufficiently structural to withstand lateral forces needed for adequate attachment. Which is why you can't find any attachment method, as it isn't recommended.
Sounds like you made your own decision on your approach to the problem. Unfortunately if someone gets hurt because the railing "let go" who would be at fault?
My suggestion is to reinstall new posts either through the decking and attached directly to the underlying joist or surface mounted outside the decking perimeter with carriage bolts(zinc coated). The Aztec decking "will" shrink with time and loosen any type of nails attached, so think about that.