[Retros] 1NAi (18 pieces)

[Olli Heimo]

Hi! I wonder if it can be done with 18 pieces like:
8/8/8/2PPP3/Q1PkNR2/RBrP4/pPrPP3/K7 14+4. Add one unit. Intention is to add wNb1. Have I missed something? It may be possoble to reduce to 17 pieces. Olli.