I've had a couple of issues recently with using the tinyint datatype in SSIS.  In one case I have a Lookup Transform which joins to the incoming data flow path on a column defined as a tinyint in the database.  The column metadata in the data flow is DT_I4, a four-byte signed integer.  Dragging this across to the tinyint column in the Lookup gives me the following error:

The following columns cannot be mapped:
[DataFlowColumn, LookupColumn]
One or more columns do not have supported data types, or their data types do not match.

By process of elimination, I discovered the incoming column needs to be converted to a DT_UI1, a single-byte unsigned integer.  One to bear in mind for the future!