Sitting here in the UK (where we have no meaningful rating system for club players) I love reading your 'what NRTP is this guy' threads.
Obviously they attract a lot of WUM's but, even ignoring them, I find it interesting how varied opinions are. And I think this could be because the NRTP tries to apply a linear scale to a logarithmic problem. At the lower levels (NRTP 1.0 to 4.0) it seems to work pretty well without too much disagreement and just from reading the definitions I am pretty confident that I am a 4.0 singles player who could probably mix it at 4.5 doubles given a half decent partner. But then it tries to bunch a whole range of abilities into a small (4.5-5.5) range. When I look at the stronger players at my club I find it impossible to categorise them within this range. I know the best guy is a 5.5 (because he is having played no 1 singles for a decent US college team). He is enough ahead of the others for me to be confident that they must have a lower rating. But from there fitting the next best 10 guys (who are enough better than me to make them at least a level up) into the 4.5-5.0 range is just impossible. The variation in playing styles and level is pretty large and you cannot split them into 2 groups - a bunch of 4.5's and a bunch of 5.0's.
So I think what you need to to take the 4.5-5.5 range and spread it out. I did see an alternative rating system somewhere which went up to 13 (I think) and gave the NRTP equivalents for each level. But it split the NRTP down to 4.75 etc. in order to do that.
Obviously they attract a lot of WUM's but, even ignoring them, I find it interesting how varied opinions are. And I think this could be because the NRTP tries to apply a linear scale to a logarithmic problem. At the lower levels (NRTP 1.0 to 4.0) it seems to work pretty well without too much disagreement and just from reading the definitions I am pretty confident that I am a 4.0 singles player who could probably mix it at 4.5 doubles given a half decent partner. But then it tries to bunch a whole range of abilities into a small (4.5-5.5) range. When I look at the stronger players at my club I find it impossible to categorise them within this range. I know the best guy is a 5.5 (because he is having played no 1 singles for a decent US college team). He is enough ahead of the others for me to be confident that they must have a lower rating. But from there fitting the next best 10 guys (who are enough better than me to make them at least a level up) into the 4.5-5.0 range is just impossible. The variation in playing styles and level is pretty large and you cannot split them into 2 groups - a bunch of 4.5's and a bunch of 5.0's.
So I think what you need to to take the 4.5-5.5 range and spread it out. I did see an alternative rating system somewhere which went up to 13 (I think) and gave the NRTP equivalents for each level. But it split the NRTP down to 4.75 etc. in order to do that.