Off the top of my head, isn't the 2004 / P17 the HW40 clone?
Worth checking the bits already mentioned.
I don't have the time right now to search out the posts and share the link, but I seem to remember there being a very detailed thread on the Pyramydairblog about stripping and improving the P17 / 2004 as well as a comparison to the '40. There may well be seal sizes there too.
Maybe I'm dreaming but I think I can remember a post by Todd Cooper on the HW40, too, which will have been very detailed.
Hope this helps.