[Pharo-project] a problem with a MorphTreeMorph with headers

Hi, I have a problem for an application I have: I'm displaying a MorphTreeMorph who has a header and some columns, problem is when morph has a horizontal scrollbar and I need to go down, last element on list is covered by horizontal scroll bar and customer can't see his data. I need to solve this, but I don't know how, any help will be really appreciated. (the attached image shows my problem) thanks, Esteban