Input Parameters Conflict

Hello Everyone,

I am new to python scripting in grasshopper.  I have written a script which preforms Boolean operations on a solid block.  I have been able to successfully run the script using the rhino python editor, however when I attempt to run the script using grasshopper I am getting a solution exception run-time error.  I think this has to do with the inputs I am using in grasshopper as that is the only part I changed.  When I change the "BackSide" input hint from ghdoc to surface the error I get in the GH python tester changes from an error in line 40 to an error in line 72.  But I cannot seem to find the proper combination to get all parts to function.

Attached are the .gh and .3dm files I have been testing with.

Thanks in advance,

Peter