The ct % hasn't been discovered or known by any normal player i guess,as i noticed on aga's thread and some other sites,just the interval and other stats,but nothing about ct,as i know,the 2x ct chance is less then 1%:)
A amount of ec to get 2x ct on every piece, average 10k-15k /piece ,around 50-75k +- 20k
If u get lucky,u can do this in 10k,unlucky,mmm200k