I have never encountered that problem. Like I mentioned before, it comes down to being confident and realizing that most of them have been instructed something to the effect "We only accept cards that display the Union Pay logo". Your modified card will satisfy that rule. The rule says nothing about how the logo is affixed to the card.

I don't mention anything or make any deal out of it. Just hand them the card like I would any local card and let them see the logo on their own.