what are recommended exponential rates for 3D and patter flying ?
i want it on my YAK 54 with os  55 ax

Expo is always a matter of personal preference, and is highly dependent on the flying characteristics of the aircraft you are flying.  I guess that is why no one really took time to respond to this earlier, as there seems to be no ONE answer to something like this.

Slightly off-topic, I always found that expo is a better way to deal with a wild aircraft than using dual rates.

i case of your yak a 50% expo on the rudder and elevator is a safe bet to start with on 3D. you may then decide to increase or reduce as the case may be during your test flights for expo check.

While it is mostly a matter of personal preference, isn't expo on ailerons generally more important/helpful than expo on elevators/rudder ?

Presumably because, for 3D, the rudder and elevator are used the most (and of course throttle).

I do not fly 3D but find expo on rudder very useful - particularly on tail draggers - for improved ground handling.

Yep, true for 3D.  But I would assume wild throws on ailerons may still take the fun out, even for 3D flying.

Wild throws on ANY control would have that effect!

And I too prefer expo to dual/triple rates.