Would Newtonian physics affect spiritual beings? I mean, they stand on solid ground ten feet above said solid ground, and can't comprehend how humans can construe that as flying. And the less said about Ikkaku's bankai on that matter, the better.

The only person to use an unwieldy sword with a physical body thus far is Ginjo, and the mass of it was something both sides acknowledged, as it limited his attacks - or would have if there hadn't been that second hilt he could use to change up his timing and range options.

Or... is Ichigo now a physical Soul Reaper? I didn't notice him leaving his body during the transformation during the fight with Ginjo.