Before I go through all these wild gyrations, I want to know of what concrete benefit will I have if 4.2A has been working fine. Although there could be some bugs I haven't found yet.

The other question is whether 4.1B and 4.2B have to be present for any future upgrades.

AJ ?
pa4X 76 ,SX900, Audya 76,Yamaha S970 , vArranger, Hammond SK1, Ketron SD40, Centerpoint Space Station, Bose compact