PASAT, a working memory test: add up the last n digits presented to you sequentially (cognitivefun.net)

I am interested in fellow readers's performance, as I would assume everybody here is fairly above average in terms of WM capacity and math ability. It turns out this test is surprisingly hard. Nobody seems to have made it beyond n = 4.

A warning, this test is flash-based. A disclaimer, I am the site creator.