That's about right for a 5 level increase. i120 would be 47 and 33. I think the OP is more interested in what happens with weapons that are carrying 3+ stats. I would assume that each stat would get a 1 point increase if there was 3 stats for the 5 level increase since there appears to only be 3 stat points to distribute. It's also possible that the first two stats would increase at +2 +1 rate and the third stat wouldn't change for the 5 level increase, in which case a ten level increase would be +3 +2 +1