Do Penson brokers ever have special maintenance requirements for concentrated positions? Just spoke with MB Trading who say that neither them nor Penson has any special requirements, and they use only the industry standard of 25%*, and I wanted to verify if this is the case with Penson brokers all around. Included in my question is anyone knows of a case that Penson or the broker ever feels they have "enough" of a particular stock & therefore increase the margining or maintenance requirements. Thank you in advance. (* exceptions in cases where there is some major issue with a particular stock.)