I have had the need for a riser in the past when I was boring an engine's cylinder and another time when I used a rather large angle plate fixture in combination with a rotary table. So, if I were you, I'd hang on to it.....or, you could ship it to California for me.
My BP has a 7" riser. I have to stand on a step to be comfortable with most of the work I've done so far. I'm considering removing the riser, but 2 days after I do that something will come around and I'll need it.