Hi, no problem using Primo or even UL Heads. They can be used without any limitations regarding the flash duration. The flash duration is controlled via the electronic cut off circuit in the pack. Here are the exceptions, as far as I know:
Pulso 8 Head is not recommended and will only work on outlet three of the grafit packs (no flash cutoff, long flash duration) I think it will work with the scoros but you will be better served with any other lamp base.
Litos Head is not suitable (designed for the senso pack, which has a different flash tube voltage)
In addition, keep in mind grafit and scoro packs don´t check the maximum rating of the lamp bases, so you will be able to overpower 1600Ws heads. With the scoros this can also happen unintended when dialing down flash power and open flash before the pack is ready with lowering its stored energy. The pack will then fire the complete stored energy. This usually won´t result in an instant damage but will shorten tube life significant if applied regulary.
Not sure, do the Primo Heads have a build in fan? Scoro packs are cycling extremely fast, don´t overheat your tubes! Remember, broncolor developed a new flash tube that is able to withstand the higher demands that can happen with longer flash series that can now be achieved with the scoro packs.
HTH.
Cheers
Ulf