Oh my. Now that is teeny tiny ribcage, large stripper breasts! I don’t think your bras would fit little tiny me. And I now feel much better about having 30 bras to try on at Nordstrom.
44L does fit, barely in a soft cup bra. For an underwire I would want a larger cup.
Apparently, my perfect size lies somewhere between 38C and 36D. Supposedly, they are the same size, but the C is too small in the cups and the D is too small in the band. 38D, you’d think would fit, but i can’t fill the cups quite right. Too bad nobody makes a 37D. lol
Weird bump of an old thread but, what the hey - I’d wear that bra, espresso_dreams. Sounds like it would fit me too! 
My best fitting bra is a Playtex 18 Hour comfort shoulder blahbidy blah. It has no underwores and seamless cups. I like the line it gives me under most clothes. It’s black. I bought a white blouse to wear on an job interview and decided that none of my not quite right bras were quite right underneath it. I went to the same store, and bought the same bra (same style number and size) in white. It didn’t fit at all the same. Grrrr.
Since wearing the wrong bra is something that really doesn’t affect anyone but me I’m not inclined to spend any of my limited budget to address it, but when I win powerball/publish the next Harry Potter/get a surprise inheritance I will go to a specialty store, get properly fitted and buy a bunch.
As for how hard it is, I’m an uncommon combination of plus size with B cups. Most stores don’t keep a lot my size in stock. Online works best.