Dynamic brake "jolt" when engaging

[chrisell]

Yes yes I know dynamic braking isn't exactly brilliant in RW but something's been bugging me for ages on my own models. It seems that when I go from traction to dynamic braking, I always get a hell of a "jolt" as the dynamic brakes kick in. I've noticed that none of the US engines do - they have a nice smooth spin-up of dynamic braking effort (looking at the hud with F5). I've faffed around with various values from time to time but never solved why my engines get the sudden face-slammed-against-the-glass jolt as they engage.
Anyone have any ideas what I might have missed either in the engine sim blueprint or the dynamic brake vs speed file?