I bought this sander and tried it on a group of pine butt jointed boards.  It is too unstable.  It tends to tip at the slightest opportunity towards the motor side.  Even a slight pressure on the back causes a gash in your work.  I spent more time removing scrapes and gashes than smoothing my work.  Very frustrating.  I am going to try a different brand as the others seemed to be more stable in the store and didn't tip so easily.