I’m not so sure about that. I removed the stock switch box from under my PD444 and substituted a thick, dense wenge wood subplinth that projects forward as a subplinth for a third tonearm mounted to a Micro Seiki brass tonearm board. The big surprise is that SQ was improved for the other two arms mounted to the stock tracks. The subplinth must be acting as a sink for vibration.
I know some people replaced stock feets, but for me LUX 444 works fine in stock condition, i like it better than my SP10mk2. I wouldn’t add 3rd tonearm as i have two LUX PD444, so already 4 tonearms :) However, i’d love to replace side pannels usign some nice wood.
Do you have a picture of your modified 444 ?