After 3 weeks from my initial request, Overdrive has my parts awaiting for payment and is ready to be shipped. Seems they request multiples just fine as long you explain how many Valks you have.
Requested:
4 x 1/60 VF-1S Roy Ver Arm Parts(2x Left, 2 x Right)
1 x 1/60 VF-1S Roy Ver Head Part
1 x 1/60 VF-1A Hikaru Ver Arm Part (Left)