@YorkshireLion: it looks to me like Ack filtering is primarily for when you have a large difference in download vs upload speed. The upload speed limits how fast you can send Acks, and this limits how fast TCP will let you download. So downloads suffer if you don't send acks fast enough.
If you have low upload speed compared to download then you can prioritize acks and the download will not stall.
Since you have a ratio of 60/17 = 3.5 I doubt that ack filtering will help you much.