Quoted from LTG:Or cut a heat sink in half and put part of it on both.
Please don't do this, this is NOT a best practice and you will actually be reducing the heatsinks ability shed heat from both your 5V and 18V rectifiers
Please look over the PinWiki page on this.
https://pinwiki.com/wiki/index.php?title=Williams_WPC#Failed_Bridge_Rectifier
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