Every time I have read an article about chipping banana seeds they do it along the side. With the micropylar plug flat on the table, just nick a small slice off of the side, slicing straight down towards the tabletop. I find a scalpel or a razor knife work well. The important thing is to place the scarified seeds into aseptic potting material, not soil. They will simply rot out in soil, too many microbes find their way inside. There was a post showing this method of scarification and the results awhile back. Here is the link to the page with the attachment (second attachment):
Re: American Journal of Botany, Vol. 49, No. 5 (May - Jun., 1962)
I have attached a full copy of it and one other that may be of interest
I hope it worked
Taorking