No need for REF.
A Hoplijp 4' can be a Nasaat 3', easy, so Go loads Holpijp samples at 4' and the same samples as 3' for another stop. Along go and the releases/attacks ect.
Beauty.....
Then with ranks (see my thread about mixtures and how Martin and Lars explained the multi ranks work on a stop) we can get a mixtuur II or III or whatever.
I have here another nice one manual organ set with 10 split stops, which began with just 6 stops (M8,B8,P4,F4,Q2,Q113) available :
Montre8, Bourdon 8, Prestant 4, Flute 4, Nazard, Doublette, Quarte, Larigot, Tierce, Cymbal II
Best
Panos