Question about CP depth and Sanwa buttons

[Aberran]

Sanwa buttons say they have a depth max of 5mm I was planning on using them in a plexiglass box.  It would use two 1/8inch layers on the top but that would get me up around 6 and 1/3 millimeters if my calculations are correct.  Just wondering if anyone knows if when it says 5 it means it and I should just route away some material or if that might still work?  Around here I cannot find nor do I think I would want thinner material.

So I guess in that rambling I am just asking if anyone has some experience that has granted them some wisdom they could share with me before I go forward with this.

Thanks all