Dual power supply with two boost converters
Your circuit cannot ever work. The modules provide a regulated voltage between the output terminal and -ve lead of the power convertor. 







simulate this circuit &ndash; Schematic created using CircuitLab

You would need to have the lower DC-DC convertor be an isolated module (no connection from input to output) to make this work.

One other way to do this is to get a Boost convertor that supplies 100V output and use an electronic ground (rail splitter circuit). I've used a bunch of these to provide 75V for stepper motors ...but they extend to 120V. You could use 30V input to reduce the input current requirement.