Does anyone know how to set up the trackpad so is less sensitive to accidental clicks

often I use openoffice.org and frequently when I type and dont watch, I accidentally click on the trackpad with my lower thumb, and as a result type in an area not intended, messing up the document, I thought system preferences, trackpad would sort this out, but having unmarked “tap to click, tap with one finger” accidental click still works with one finger (lower thumb) click. Can this be sorted out?
thanks in advance