I have a shielded Danell 6-socket power strip and I would like to know if it is safe to plug in this power strip behind this APC UPS power unit (Output). I would plug in this Smart UPS directly into a wall socket (Input). APC does not recommend to plug in surge arrestors behind their UPS. However, they mention it is OK to plug in a Power Distribution Unit or PDU. This Danell 6-socket power strip (https://www.wavesafe.ch/en/power-strip-with-6-sockets-for-swiss-plugs.html) does not have a surge arrestor but only a power switch. Would it qualify as a PDU and can I do safely? Many thanks for advising.