The most important thing is the carton you use inside.
is used for isolation in the electrical industry.
The pressboard should be 0.6 mm/0.02 in thick.
Have a look at the shape of the horns (blades, wings):
Left a biretta I bought from Poland
Right a biretta from Italy
The silk pompons you need, you can order from Roman tailors. Prices are around 8-10 Euros per piece. These silk pompons (tuft, tassels) are the only ones which do not collapse and where the threads stand upright for a long time.
If you use threads which are too heavy, it looks like that: