I'm not exactly sure what you mean by "thinner" but they ARE different...you bought white ones, instead of the ones with yellow background?
The OLEDs you've put in may not be the exact same size or resolution as the yellow ones that were originally installed on the deck.
I would get two more new white ones because if those yellow ones are original, they will die soon.
There's a definite life expectancy of them (about 40,000 hours set at half brightness), and most of it was used up when they were ON in the casinos 24/7.
Do the math....8,760 hours equals 1 year....except a leap year...lol