I like the looks of these pistons but I would think it might be a good idea to smooth the tops to prevent detonation. Maybe @yellow rose, or @rumblefish360 can chime in with a recommendation. What say you @RustyRatRod, or @krazykuda ?
The only way I know to know for sure is to do the .500 downfill and then you'll know for sure what you have. I do have an old DC manual around here somewhere. I'll dig it out and see what I can find.