Digital BW, The Print

I've just received my 4800 printer with photo black installed. The prints on glossy are great, but of course the black ink swapping issue is there as now I'd like to make some matte prints.

I found this article on how to swap the black inks with much less waste:
http://www.northlight-images.co.uk/article_pages/printer/4880_swap_black_ink.html

Did any of you try it in a 4800?

Hoe many pages of black did you need to print to clear out the old ink?

I guess I'll just go ahead and try it and see what happens...