Well, for anyone who wanted to use this on their server for old race/class modifiers, it appears to work properly. Here's a table of test data, where the experience numbers are totals needed to complete the level:
Code:
Wood Elf Druid (0%)
Level 1 - 1000xp
Level 20 - 8000000xp
Level 40 - 83200000xp
Level 59 - 616137000xp
Human SK (40%)
Level 1 - 1399xp (+39.9%)
Level 20 - 11199999xp (+39.9%)
Level 40 - 116479998xp (+39.9%)
Level 59 - 862591785xp (+39.9%)
Iksar SK (68%)
Level 1 - 1680xp (+68%)
Level 20 - 13440000xp (+68%)
Level 40 - 139776003xp (+68%)
Level 59 - 1035110183xp (+68%)
The 40% penalty turned into 39.999%, which over the course of 60 levels is 15xp. I think that's acceptable. The client (Titanium in my case) appears to sync percentages properly, also.