Butler Creek Cap Sizing For Diamondback Tactical 6-24

I've measured both the objective and eyepiece and have ideas of what I need, but I wanted to see if anyone had practical experience with the Butler Creek's on this scope. I've read folks recommend both the #39 and #40 for the objective, and the chart on Butler Creek's site is dead on with a #18 for the eyepiece. I personally like a very snug fitting cap, leading me to think the #39 is right, but I'm sure we all have had the same issues over the years with what should fit actually fitting.

So does anyone have Butler Creeks on their Diamondback Tactical 6-24?