As far as I understand, in an SE/30 with a CPU accelerator present, once boot-up is complete, all processing is taken over by the CPU on the accelerator. In that case, I would assume the correct place for an added, fast FPU is on the accelerator card itself, not on the adapter card or any other PDS card, and there should be no conflict with the motherboard FPU if present. You are correct in that there is no need to add one to an unaccelerated system - hence, I assume, the fact that they are socketed rather than soldered down to the PDS cards.