Yeah.... and sorry, but as you can imagine, there is no way I can just trade people for the $8 dollar difference. That would kill me! The copper is expensive. Plus it is harder to work with.
Quite honestly though, the aluminum heatsink in this build is really just fine.
The copper is better, but not completely necessary. With an 8X build, it would be desirable for sure.
About duty cycle. I know that Igor has been doing some testing on duty vs no duty, and I don't know enough to just recommend 'no duty cycle'.
I have a habit of using a duty cycle. But I'm sure that it mostly depends on the current setting. For instance, I read more than one experiment with PHR's, that at 90mA's or less, they can run for days or even over a month in one experement with no heatsink!
tbd2001_01, I sent your Pocket Mini kit with 'Hot' option (and other items) today. (Thursday)
Hope your build goes well!