Manually specifying candidate masters in Maxscale

Looking over the documentation, I haven't quite been able to find if its possible to manually set the candidate master status of a server in Maxscale. The reason I am looking for this is because some of the slaves we have hooked up the the master/slave server architecture have inferior hardware to the others, and we don't want them to become the master. Looking at the documentation, it is possible to set the status of a sever as master or slave, but not specify that we don't want it to become a master. Is there a setting to do this in Maxscale? Possibly in maxadmin or a .cnf file or something? Thanks.