We use the LNK304 for our design. We based our design on your RDR-138 Application Note. Actually, we have some problems with the UL approbation for our PCBA. The C1 and C2 4.7uF/400V electrolytic capacitors are the problem. It seems that UL agents want to force us to use UL approved capacitors. We already saw your note in the forum about it (https://www.power.com/forum/low-power-design/do-pi-parts-have-ul-csa-or-other-safety-agency-file-number/) and we have a SMT fuse before the capacitors (the single fault test should be OK regards the forum comments). So, do you have a technical ressource to help us to persuade UL agent to use standard electrolytic capacitors?
Note that we are in preliminary approbation. We sent the schematic for evaluation.