Interesting jt... the old P-charts were still in use in NZ until relatively recently, with nothing really significant provided since to replicate the calculations they provided. To my way of thinking, they should be able to be reproduced electronically -if the calculations/factors used in producing the charts are still available/published somewhere... and quite a bit of time spent getting them sorted. From memory (I don't have an old P-chart to refer to) most of the factors should have been fairly linear... so fairly easy to reproduce. Others would require a bit of mathematics...
Any idea where I would be able to source the calculations used to generate the charts? And the fudge-factors too? I'm assuming the fudge-factors for most aircraft (light singles/twins) were fairly common across the board? Would the fudge factors have been used predominantly to allow for the differing skill-sets of various pilots likely to operate the airframe, weighted towards the lower end of the scale?