Some food for thought for you:
The specific output numbers will depend on machine/ink/media combination. But that really isn't a designers concern.
There are two ways to accurately specify Reflex Blue in a design.
1) Using Postscript labelling - use the built in Pantone Swatch book, and leave it as a Spot. Save in a file type that supports Postscript. (There are some headaches with this where transparency layers and effects are involved, but the theory is right!)
2) Work in a colour space that is large enough to encompass Reflex Blue. (HINT: The default AdobeCS CMYK space does not.)
If you create an artwork in the default CS CMYK space (US Web Coated SWOP) then it doesn't matter what combination of CMYK percentages you use - you can't specify reflex, because it's not within the gamut of US Web Coated SWOP. You'll bash your head against that for ever.
So there are two places that you can lose your reflex blue.
1) Manage to specify it correctly, but then try and have it printed on a machine/ink/media combination that can't reach it.
2) Fail to specify it correctly, and have the dull blue colour you actually specified printed on a machine that could have hit reflex blue if only you'd actually asked for it.
This applies to all sorts of colours that push the gamut of some output devices. That's actually the core logic behind the work I do with customers advocating a large gamut workflow. Start with something that lets you specify all the colours you could possibly want, and then look at the limitations of the production methods for the application of your design. Rather than start with something that limits the colours to a small selection well within the capabilities of most current production methods. That's what those designing within the confines of the AdobeCS default spaces are doing. (whether they know it or not.) If you've never changed the defaults... this means you!
This 1st article is about this subject -
RGB or CMYK? The CMYK habit discussed! | Hudson Don't be put off that it's discussing RGB vs CMYK - the point is really about designing within a large gamut rather than limiting unnecessarily in a small one.
This 2nd article is the theory put to practical use -
Hudson's Edge - Colour Space | Hudson
Don't get too hung up on the percentages you specify in the artwork UNLESS you understand the answer to "the percentages of what exactly?" They're just percentages, they mean nothing at all on their own.
Hope that's useful to someone. If any designer wants to test these ideas and report on this forum what they find, I'll be happy to oblige. Message me.