Let me clarify. I sorted out my problem with the tapered spokes. Yay me. There never was a problem creating a single solid using booleans.

See screenshot. The red arrow points to an area where the fillets need to be very heavy *between* the spokes but not as heavy at the top and bottom of the spoke. I'm sure it's a blend or network or something else I also don't know how to use.

3dm file lives here for your viewing pleasure: https://www.dropbox.com/s/kkldadi27wf7y0t/NYC%20999%20tender%20wheel%20v2a.3dm?dl=0

Thanks

Chris