I already thinked about mailing the support about this, I just tried here hoping someone would have been in the same situation !
Basically I am interested in keeping 2 full single sabers to build my double because I am interested in being able to divide into single sabers for duelling, and making it a double for "aesthetic" purpose (cosplay, ...). In this consideration, logic make me think it would need 2 assembly packages because I assume it was primarily designed for building 1 single, not a double which is actually 2 singles.
I thank you for your answer
I am going to mail the support about this question, but I am keeping watching this thread in case someone else encountered this situation.