I'm not a Rodinal user but I suspect most people would use Pan F+ with Rodinal diluted in the 1+100 range to help tame contrast. The decision to downrate it really depends on how much shadow detail you want and how much contrast you develop to. Rating it at 25 sounds about right but that would be for my taste. Others might disagree.
Personally I'd tend to lean more in Gerald's direction but it really depends on what kind of tonality you prefer, how much grain etc. I go for the best balance of fine grain/sharpness I can get, and for me that's not Rodinal, mostly because I have never found Pan F+ to be as fine grained as I expect for its speed. So rather than use Rodinal I prefer dilute solvent developers such as XTOL 1+3, ID11 1+3 etc. At these dilutions general purpose solvent developers are essentially as sharp as Rodinal, but finer grained. Tonality is a little different than Rodinal but this can be adjusted/manipulated. I'd use D23 in the same way (1+3). At stock strength or 1+1 I have not personally found D23 to be a low contrast developer, and it would be less sharp than Rodinal at those dilutions too.