jan plas subject has been discussed many times...in brief the chronology is going as below:
-due to kyokushin karate there was a strong contact between holland and japan and plas was also one of kyokushin practicers and in one of his visit he met kurosaki and influenced from "japanese kickboxing " too much (at that times "muay thai" has become this new name and format although it has started in the beginning as muay thai )..and after return he opened "the mejiro gym" with permission of kurosaki who was the owner of "mejiro gym -jaqpan" ...and plas was very successful since he brought a new dimension and dominate all the dutch kickboxing scene and created big fighters like "kaman, carbin, royers,yamalı,brilleman" in modified mt and kickboxing...i remember those days when the mejiro fighters beating all the other gym fighters including also "chakuriki"...however , plas'name have been put into a "kidnapping or something like subject" and he went to prison ...at that time "manaart" got the the control and mejiro slowed down since manaaart was just a fighter and hadn't big experience as trainer...at this point "thom harink" came to the stage and began to dominate the scene...
however, those dutch champs have been good in "modified mt as at that times it was called as kickboxing and also in "low kick full contact" ...they also got some success in front of some thai fighters ...however, you should to consider that none of them could beat the best thais (lumpini or raja champs) in muay thai in spite of weight cathegories...
after his freedom plas preferred to stay in japan (wrestling) and now we see him at the corners of the dutch fighters...he was a very open minded trainer at his times...
-kurosaki, i did only to touch that he is very traditional in training methodology and sticked on old training methodologies too much...otherwise, of course he has done new things , he was one of the pioneers to convert "muay thai" into "kickboxing"...