I'd look into getting nice bolt on hub-centric spacers done. As long as you're not in the bodywork, there's nothing wrong with that as an installation.
Most people don't understand how the lugs work - the bolts themselves don't carry much shear load. The load is carried by the friction between the back of the wheel and the mating surface. As long as you can come to torque, there will be no difference in the the clamping force no matter how wide the spacer is.
I wouldn't stack multiple spacers for any kind of permanent installation (I know that's not your plan; I'm just putting that out there for anyone who might be reading this). At some point you do start to turn the stud into a lever. Bolt-on spacers take this into account and are a single piece.
Most people don't understand how the lugs work - the bolts themselves don't carry much shear load. The load is carried by the friction between the back of the wheel and the mating surface. As long as you can come to torque, there will be no difference in the the clamping force no matter how wide the spacer is.
I wouldn't stack multiple spacers for any kind of permanent installation (I know that's not your plan; I'm just putting that out there for anyone who might be reading this). At some point you do start to turn the stud into a lever. Bolt-on spacers take this into account and are a single piece.