rexrainbow - sorry I missed this thread (you typo'd my name so the forum didn't alert me)
Your proposed solution is correct, if you modify the SOL for an object, calling objtype.applySolToContainer() will set the corresponding SOLs in the container to have picked the instances corresponding to objtype. However, it's not particularly fast and should only be used in one-off places, like system's Create Object. If it's performance sensitive it gets a lot more complicated, but hopefully that call is enough for all your cases.