EFII System 32 - Bus Manager Alternator wiring

[JoopSJ]

I need some advice here, as there is no guidance on this by the supplier:
I have the Bus Manager, Two batteries, B&C main and stby (vacuum pad driven) alternator, both with external voltage regs, LR-3D.
The drawing depics the current situation:
The Main Alt supplies power to both busses and battery 1.
Battery 2 is charged by the STBY Alt. To get that, the Bus Sense is picked-up at battery 2 positive terminal.
The problem I have with the current setup is that, when I depart with a weak Batt2 (I know I shouldn't), STBY Alt goes up to its limit of 40AMPS to charge the battery. I don't like this since I have no blow-tube on the alternator and am fearing overheating it.

I am looking for a setup so to let MAIN ALT to charge both batteries and save the STBY as a real backup, but I think it isn't possible considering the diode setup in the Bus Manager.
Anyone can share how they hooked-up two batteries and two alternators (with ext volt reg) ?
Please note that the blue diode in the schematic is removed when installing dual alternators.

 

[dmattmul]

I've been running a very similar set-up on my 14 now over 7 years. The diode protection allows the main alternator to feed the main bus and engine bus, but the engine bus cannot feed the main bus because of the diode protection. I would regularly turn off my stand-by alternator, and the engine bus would drop from the ~14.3 volts down to 13.8 volts and hold. The problem comes in when the primary was turned off the stand-by can't feed the main bus due to diode protection. On the 10 I installed a cross-feed contactor that would allow the engine bus to feed the main bus when switched on. Z-14 (https://bandc.com/wp-content/uploads/2018/05/001-507_z14_revB.pdf) does a good job documenting this. With the cross-feed on the back-up does feed the main bus. I believe the bus manager was designed when back-up pad mounted alternators would only output 8 amps so it was impossible to use it to feed the engine bus and main bus and if one tried you could exhaust both batteries rather quick.

If anyone has a better understanding of the Bus Manager please give your input, I'm a Chem E not an EE.