Scott,
as you will have found out by now, I have not produced any hard rules or formulas about batten scantlings. That is because I find it too complex to produce any formulas. Instead, I record what I have used, how it worked and then try to interpolate or extrapolate to get the scantlings right on my next project.
My guess is that the 25 x 2mm tubes would be fine on the lower battens of your boat. However, batten 2 from top should be of the 1.5” x 0.065”, as it takes a much higher load than the others. It might be an idea to use that dimension for the boom as well. One may be tempted to use the strongest dimension throughout. However, I have found that although these big-diameter-thin-wall battens are great for stiffness and strength, they also result in a quite bulky furled sail bundle, so moderation in all things.
One more thing. You are using 6061-T6 alloy which has almost twice the yield strength of the 6060-T6 I use on my battens (I only use 6082-T6 on my masts), so I am pretty sure you will be fine.
Good luck!
Arne