We are going to use A5 and A14 for FM1 and FM2. (The role of these two can be swapped)
The reason for the selection is the better perpendicularity among the available prisms.
A11 has the best perpendicularity among them. However, the T didn't match with the others. The pair of A5 and A14 has a good matching with small compromise of the perpend.
The attachment is the excerpt from T1500060.