^^^ responding to the last 2 posts...

While 48/30 (18t gap) is beyond the Shimano 16T FD spec, I have tested it with the UDi2 FD and it seems to work fine. Ric's "super compact" setups typically use 53/34, a 19t gap, though he may favor SRAM FDs for those setups.

Needing to shift rear gears when changing the front ring is no new thing, I do that all the time with mechanical shifters. Lastly, the range of gears we use and preference for tight combinations, does not require a triple front, a double is plenty. In fact, with a 48t big ring we will be using much more of the middle "sweet spot" on the cassette than with a more typical 52t or 53t ring, plus much less shifting front rings than with a triple setup. On the very rare occassion when a 34t cassette is needed, we'll put up with the XT 11-34 (or modified to 12-34) cassette.

Gear selections are somewhat a non-factor to the technical SSD question at hand. With both the big ring + Gates ring mounted to the same 130BCD spider, I could see a monster power team maybe shredding the spider if they overloaded it with massive torque. We don't fall into that category and I suspect these cranks are spec'd to easily handle the ~900 peak watts I figure we can generate for short term efforts.

We never once dropped the chain to the outside on our tandem with the 6703 FD. When setting up the Di2 6770 FD that initially did happen before it was adjusted properly. No harm done, there is insufficient room for the chain to jam between the belt and ring. It actually appears to be a nice chain catcher if that ever happens again (unlikely when the FD is adjusted properly).

I like the inner shape of the FSA "Super Road" big ring shown. Those outer rings have a curve built into them, which probably helps shifting up from a compact setup. Unfortunately, FSA does not make those rings in a 48t. The TA rings are perfectly flat, but the pins seem to get the shifting job done nicely.

I never seem to get a precise alignment with my cheap drillpress, so I would not want to try machining it myself. Perhaps my LBS or machine shop could, I'll need to check.