I recently got a few rolls Velvia 100. I read throught the datasheet and it state that the film can be pushed to 400. Does anyone has tried to push the film to 400? If yes, can you share the picture quality at 400 with us?

Another question not related to Photography. I am going to Taman Negera soon. Can I wear my army boots there, and is it OK to wear the No4 trousers there? I understand that these items are sensitive, I am not sure if they are still so sensitive nowadays. Please advise.