The opening at the bottom serves to avoid dirt accumulation and to prevent a stored 58mm tamper from getting wet.
The model is optimized for a layer height of 0.3mm, with a 0.2mm height for the first layer. The infill should be rather high so that the stand is heavy enough not to tip over due to the weight of the massive ECM portafilters. I printed it with 95% infill and 4 perimeters with a 0.6 Nozzle to get it heavy enough. The final weight of the stand was 200g which was still not enough.
Therefore I added some holes at the bottom to glue in some 20g weights: https://de.aliexpress.com/item/1005006467817749.html?spm=a2g0o.order_list.order_list_main.107.6da75c5ftROJTd&gatewayAdapt=glo2deuhttps://de.aliexpress.com/item/1005006467817749.html?spm=a2g0o.order_list.order_list_main.107.6da75c5ftROJTd&gatewayAdapt=glo2deu
Final weight with lead is 291g for the one I built for myself, this is enough not to tip over
The author marked this model as their own original creation.