Hi,
It sounds like what you have created is not a "Matrix Structure" but just divided the reporting relationship times for an employee. Actual Matrix structures are created in PPME after defining them in table T779M and usually define different relationships - such as dotted line reporting or project assignments.
Also not sure what you are gaining by saying the person reports 50% to HR and 30% to IT. Question is - who approves the employee's pay increases? Who approves the employee's time off? Does the IT Manager really only approve 30% of the pay increase? What you probably mean is that the person's time should be charged 50% to HR and 30% to IT. This can be done via IT0027 to divide the person's time over various cost centers. Or you can use IT1001 to assign the cost centers and percentages to the position.
You said you used PP01-General maintenance. Thus, the question - which relationships did you apply the percentages to and which transactions and views are you looking at?
Paul