After some quality checks on the pre-perforce history, I decided it would be worth running through the import of the 5.003_08 -> 5.004 series again, but this time with a little more patience. When I ran through it at the reposithon, I was accepting all the defaults and decided that I'd written too fancy an interactive importer to let that be the case.
Some people might wonder why the importer needs to be interactive, let me say that I'm making dozens of minor corrections along the way. There is a lot of manual work going into it!
Just today, I've managed to extract another 29 commits out of the 5.003_07 -> 5.003_21 phase of the history, bringing the total from that period from 200 to 229. This might sound minor, but taking the higher quality of the conversion into account I'd say I'm increasing the detail and resolution by about a third to a half.
However, I am pretty much on a roll with it, and hope to keep going all the way through to the end of about 5.004_04 very soon, which will give a very firm base for putting the Perforce history onto. Thanks to Robert Spiers and John Peacock, I now have a Perforce repository with the metadata extracted. It will be worth doing some re-work of the Perforce importer to get it clean.
I'm trying to get the project listed on OHLOH - but OHLOH seems to be having some issues. I have written to the maintainers of the site.