Using Kid for 24 to 12 converter

[ClassicCrazy]

I did some solar reconfiguration today. I had three independent solar systems and controllers . In the end I combined two split 24v systems to run the Classic at rated 2700 watt capacity. I had been using the Kid on a few panels to charge 12v AGM batteries for 12v loads.  Now I ran 24v from Classic system to Kid to charge the 12v batteries. I turned battery amp limit down to 10 amps for now.

My question is should I be using Solar mode ? Or would one of the other modes have more advantage for what I am doing? It seems I will just want to be floating the AGM at 13.8 since they will have all available current they need to run their loads. So I set float and absorb to 13.8 v for now.

Ideally what I think I would like to do is to use Classic AUX to run relay that will switch Kid 24v  charging input on when Classic has extra power . Then I can put standard absorb , float settings back in Kid .  Maybe next weekend I can tackle that end of the project if I can dig up the relays I know I have around here somewhere.

Does anyone have any suggestions or does this sound like an okay setup ?

[ClassicCrazy]

I am trying to calculate efficiencies of this setup.

If I look at what is happening right now
Load 0.9 amp  x 12.9v  = 11.6 watts with no input to Kid
turn on 24v input to Kid
3.0 amp in x 14v  =  42 watts 

42 - 11.6 = 30.4  watts

From classic Kid load is
3.4  amp x 25v  = 45 watts

30.4 / 45  x 100 = 67.5 % powering efficiency powering load

Classic reads 25v battery , Kid reads 24.4 v input from battery so I have a voltage drop though have not compared voltage readings on a meter of Kid and Classic - been using their screen readings.

I believe I did all these calculations correctly.
What I conclude from this is it would be better to shut off input to Kid until solar is available to charge  instead of supplying constant float charge.
The efficiency calculation is probably effected  by loss from the old AGM batteries on the 12v system too.

[ClassicCrazy]

I put a better battery on this and think the efficiency is going to show a lot better value - but I didn't have time to test and calculate it out. 
My next test will be to turn on the ham radio's and see if there is much RFI noise . I will be able to shut of the Morningstar Tristar MPPT controller now - which I know makes lots of noise.