An advance curve with your springs need not have 'hundreds of variables'. Don't include vacuum advance 'cuz that factor is not pertinent to the springs. Cam slot length need be only 'enough' to exceed normal requirements. 'Most' setups will have around 20 crank degrees centrifugal coming from the distributor. Run a chart to 22º or 24º to cover some excess. Initial spring tension would matter, but for a 'baseline' use a distributor that hasn't had its perches tweaked. That would not cover everything but the keyword is 'baseline'. No one with any sense is going to change springs in their distributor and not tune the ignition system to perform as they want it to. With any spring change one still needs to know where the curve starts, how fast it ramps up, where it stops. Initial tension will have to be sorted, slot length will need to be set.
It's all part of the process isn't it?
With baseline curve information I could get an idea that I'll get to 20º crank degrees at, say 3000rpm...or 2800rpm. I'll find that out after I put the springs in anyway, but it would be nice to know, ballpark, what to expect.
Besides, put a 'YMMV' disclaimer on the chart and all bets are off anyway! ;)
Something simple like the chart you show in the pic above would do...with a bit of clarification; 'fer instance mark on the 'X' axis better where the rpm numbers are. The somewhat vertical line where '3000' is noted is evidently not the full advance number 'cuz that number is noted to be 2500rpm. OR...is 3000rpm where the kind'a backwards looking square root sign is pointing? Plus, having two springs constructed as shown will lead to a two-stage advance...which I don't see on the 'My Hoppy Springs' graph shown.
