Hiya.
Color me surprised, but I just spend about an hour (or less) writing up a one pager that has ideas for using a more "simplified" resolution for HARP. I know there was that whole "d20ified" document, but, IMHO, too much to bother with. What I did was simply 'divide/multiply' any % roll stuff by 5; rounding down for 2, up for 3. In other words, a HARP bonus of +27 is a +5, while a +28 gives a +6.
Anyway, only the "%'age" stuff really needs to be converted...as that's where the slowdown my group and I experienced when we played HARP. It started off fine, but after only about 2 hours the math was just getting in the way. Adding 7 to a roll of 12 is easier than adding 33 to a roll of 58...even more so when to get that 7 you had to take 4 -1 +2 +2, and not 18 -5 +9 +12. Toss in being the end of the night and/or a beer or Brown Cow or two and we gave up.
So...has anyone else "simplified" HARP's core mechanic to be, well, simplified?