Hello, I designed a spool holder for FlsunS1, the holder is designed to be placed on the side of the printer, in the place where the secondary filament inlet is. There are 3 holes for screws in the model, those who do not want to drill into the side of the printer can use double-sided adhesive tape. For me, this is the best solution because you can insert a holder with bearings that I made into the holder. Here is a link to the additional model https://www.printables.com/model/1234746-spool-holder . The spool holder guarantees minimal resistance when unwinding the filament, it is much better than the original solution