I have witnessed (and been involved in) four Perky line failures on models that passed the current pull test. Like other speed and racing rules, the Perky rules were written long ago before speeds reached the current levels. Speeds of 120 and 122 from a standing start have been reported. This implies a PEAK speed in the 125 to 130 range.
The current rule is 25 G's with a maximum model wright of 23 ounces, which calculates a pull of 36 pounds. It has been accepted practice to forego the weighing and pull them all at 35 pounds.
The "rock on a string" formula, VV/R, computes to 31 pounds of line pull for a maximum weight weight model at 130 MPH. Thus, 35 pounds of pull test is barely any safety factor at all. It is accepted practice in AMA Speed and Racing to adjust the pull test to the current reality. Therefore I have made an Event Director decision to go put to 40 pounds at this year's Brodak Fly In.
While this pull test could break some lines and planes, the failures will be less costly than the alternative. Without doubt, the current pull test has been proven to be inadequate.