Well...
All that aside...
If I'm understanding your process here: They really want 1505C. You've told them 1505C isn't possible by differing printing methods and have therefore steered them to 1645C, which they have grudgingly accepted, but don't like on uncoated stock, so for that you're recommending 021U.
And I say that is a horrible disservice to the client.
To start, are you familiar with the formulas of each of these colors? I'll assume you know that all Pantone colors are ink formulas, and that the formulas of all the colors are the same between coated and uncoated versions, meaning that coated and uncoated are simply representations of how the exact same ink will look printed on different materials.
021 is a Pantone mixing color, meaning that there is no published formula for it. Pantone 021 C or U is simply Pantone 021, right out of the can.
Coated or uncoated, Pantone 1505 is the color right above it on that page. It is simply 021 cut in half with transparent ink.
Pantone 1645, however -- coated or uncoated -- is 5 parts warm red, 3 parts yellow, and 8 parts transparent ink; meaning that in actuality what it is is Pantone 1655, cut in half with transparent ink.
Now, the thing is, neither 021 nor warm red can be reproduced in CMYK. But warm red isn't as orange as 021. To my mind -- and as I said -- you're chasing a unicorn here.
The client wants a color on the 021 page. They want 021 as their base color.
You're taking them down the wrong path chasing some other color with some other base when my guess is they'd be happy with 1505 if they just used printers who can run spot colors correctly. And if they don't, then your work-arounds are just going to take them farther afield.
And I'm not quite coming at this out of left field. I deal on a constant basis with large-format digital inkjet printers who want to print Home Depot orange, or KTM orange, or 021 orange all the time. In digital inkjet, how close they can get depends on inkset of a particular device and the reflectivity of a particular media, and of course with just CMYK -- any CMYK -- they can never get completely there.
But with proper profiles they can get closer than the Bridge Book says they can, and usually they're happy. However, the limitations are the limitations.
In digital printing, any spot color is a name and L*a*b* value. The RIP reads the name, then looks for the L*a*b* value of that name in the destination color space, which is the printer profile. It's all in the printer profile how well that color will be reproduced.
But what's indisputable and unchangeable is that the L*a*b* value your client wants is the L*a*b* value of Pantone 1505 printed on coated stock. That should be your starting point.
You can chase work-arounds all day long, but that's the number you should be trying to achieve.
Mike Adams
Correct Color