Nice project, and instructive.
- I like the choice of Praxis chainrings! But I can't help but think that a 50t chainring will spin out.
- If you are eschewing a triple to save weight, it really shouldn't weigh that much more. IIRC with a Lightning it is about 100 grams.
- Did you analyze with the Lightning crank vs. the DaVinci on a gram/$ basis? Since there are two cranks, and these relatively hefty, even if a crank is expensive, it can make up for a good chunk of weight that is hard to reclaim elsewhere, cheaper.
- Is a Gates drive a possibility? That doesn't save as much as claimed, but it does save some.
- The Powerdome SRAM cassettes are really light.