Non-linear should be accurate enough as when accelerating you do not need fully hard shifts unless you have that baby floored and want to get out of dodge quickly.
Partial throttle (let's say halfway) would not generate enough pulling power to warrant a really hard shift. You have to remember that it is not the speed of the engine that controls vacuum to the tranny but is the position of the acelerator pedal (at least on my 1980) and therefore is not truly related to engine output as measured by RPMs. If you floor it off the line it will have essentially zero vacuum throughout the shift range. If you lightly accelerate it wil have full vacuum all the way through the shift range. I played with multiple fittings to reduce vacuum at a standing idle just to see how the car would react with the adjustments made to the tranny and got some pretty interesting results but finally went back to the original configuration.
You can of course adjust the bleed valve to suit your needs. My wife likes them soft all through the spectrum of throttle but for myself I like to make sure there is no slippage except when accelerating just above idle.
I'm still adjusting to suit both our likes...
