Thanks for the rim weight/moment of inertia tutorial! I like your drawings.
The moment you highlighted is actually around a different axis. Ixx is the one you want, which goes through the axle. 13,880 g mm^2 sounds pretty nice for the half and it matches my intuition for the design & the rim weight quotient you calculated (which also looks correct).
The Diffraction has a moment of 14,360 and a rim weight quotient of 57.9%. The total mass is about 64.35g assembled (depends on pads/bearing used with a 8mm steel axle). It turned out really good (in my opinion) in terms of stability/etc.
Throwcafe published some of the technical specs of the boba on their blog. Here’s what they said:
The technical stuff
Each half has a moment of inertia of 14870 g mm^2 and weighs about 31g, for a total yoyo weight of just under 64g. In comparison, the Cappuccino’s halves weigh about 30g and a moment of 13700 g mm^2.
An organic shape lets you put more weight where you want on the yoyo, and here it’s mostly rim weight. While the Cappuccino’s light weight and decent stability make it a speed demon, the Boba is a bit slower, more stable, and fun as an everyday throw.