I set the offset for bpyp
bpmym to -71 mV bpmyp to -100 mV
and set up the attenation so for a NIM -800 mV input it arrives at the same level as a -800 mV signal put on axp.
Somewhat I could not redproduce exactly the same offset and attenuation for bpmyb and bpmym as bpmaxp, so I tweaked the offset and attenuator so that max signal of bpmy is same order as bpma.