Recently I acquired Noodler's Empire Red, a UK Eternal. It has no flow problems in my experience, contrary to what's been said about some of the other UK colors, but it can be a bit pale due to its eternal quality... So of course I set out mixing. Here is a scan of a sheet I've been keeping, documenting each red mixture I've made (in the pen)... Proportions are wholly unknown, but I think there's a lot to learn from here. Sorry it's not systematic, but that's the way it goes. There's not much to comment, except that the "Huashilai OK-1" is an $8 cheapo cheapo (once is not enough) pen that leaks with many inks, but is also very wet and thus a nice indicator of the maximum saturation you're going to get out of the ink/mix.
Cheers, enjoy! I'll post more once I've filled up my second page!
The second picture is a slice, so you can see it even closer, but save bandwidth. You'll have to match them up to know what's what, though.