Purchased a (heavily) used, but fully functioning, Hoverboard on Craigslist and got a chance to tear it down and take detailed measurements of battery pack, electronics, and motors. With the solid rubber tire removed, the hub motors come out to exactly 5.0" which is PERFECT for kart tires. Ended up purchasing a 10x4.5-5 slick tire, which works out to the same width as the Pint's tire, with a slightly smaller OD and 1" smaller wheel size. Also purchased a tube so that I won't have to worry about sealing against the motors. Initial CAD test-fit shows that when assembled there an approximately 0.25" gap between hub faces, which will be filled by a 3D-printed spacer, then the motors will be bolted together.

Next orders of business are fleshing out the frame design and fitting electronics, then deciding on a mounting solution for the two motors. Would be nice to 3D print mounts, but not sure how those would hold up to all the torque long term....