Used developer as C41 starter or DIY?

Hi.
I bought a 5 lt. flexicolor LORR LU kit, but I need the starter, that I didn't buy because the import taxes add up pretty quickly, So here are my questions:
Could I use some used developer from an arista C41 as a starter to season de developer?
Or, does someone know a formula to brew my own starter? from the MSDS I can see I have all the ingredients except the acid

Weight % Components - (CAS-No.)
10 - 15 Potassium carbonate (584-08-7)
1 - 5 Pentetic acid, pentasodium salt (140-01-2)
1 - 5 Sodium sulphite (7757-83-7)
1 - 5 Sodium bromide (7647-15-6)

I am not an expert, but based on what I've learned from Kodak Z-131, it would be easier to go the other way around: continue with your Arista C41 developer and replenish from your fresh Flexicolor developer replenisher.

In other words, assuming you have 1L of used Arista C41 developer, and assuming you developed 8 rolls in it, you pour 263ml out, and replenish with fresh Flexicolor.

Why 263ml? Because the replenishment table in Z-131 gives 33ml (approx) per roll for replenishment rate:

8 rolls * 33ml = 263ml

thanks! that's a good idea!