Diode oring for solar charger with dual battery isolator?
The Schottky diodes are probably not required the battery isolator already is a diode or the equivalent of a diode and the output of the solar charger can handle the charging voltage as provided by the alternator.

The solar part of the system should already have a diode in it somewhere to prevent reverse flow into the panel. 

The larger problem is that 'smart' solar chargers sometimes do not play well with other charging sources, they get confused by the voltage changes caused in your case by the alternator. This will not cause damage but could cause the solar charger to operate at less than its peak performance. You will need to check the specifications for your charger. if it is a 'dumb' pwm controller without a 3 stage charge algorithm you should be ok.