Ive been using three Delta 50-345 mobile bases for years with 1.5 X 1.5 oak for the frame.  I recently purchased a band saw and I was pleased to see the Delta mobile base still available.  The quality of this new base is at least as good as those Ive had for years.  Using oak for the frame is definitely the way to go as there is very little flexing when using oak over pine 2 X 2s.