It maybe just needs a bit of darting at the back to lie flat across the shoulders. I'm not overly fussed about costumes as long as they don't actively make the skater look bad.I liked Nathan's shirt OK. Better than his SP costume. Plus, his LP music wasn't the worst of the competition.
I don't think Nathan has much of a postural problem, he looked fine in the ISP videos of his freeskate wearing stretchy workout clothes. But on his frame, an open neckline/lower collar might work better. Anything turtleneck would have to be carefully tailored so that it doesn't make material ride up towards his neck (I get that problem with shirts too if they're too tight across the shoulders).
I really like the LP music, it's just a bit unforgiving if you make mistakes.