Smallbore,
I think your current results should already tell you quite a lot about what 'spin' does to a pattern at middle to longish distances.

I think H&H publicity regarding patterns from paradox guns needs to be taken with a huge pinch of salt. It should work well on partridges though!

As a point of interest - I assume you need permission to use a section 1 firearm on the land you'll be shooting on (even with shot cartridges)?