I know with traditional square taper bottom brackets you can get the chainline (for SS or IGH) spot on with different spindle lengths, which vary over a significant range. How is this done with hollow tube bottom brackets?
Yeah I mentioned the above. With hollowtech, not nearly as much variation allowed; I put 4mm of spacers under the right cup due to a FD interfrence issue, so on left, tube recessed 4mm more than design intent. Left arm came loose. I subsequently made mods to the FD, removed the spacers, and chainline was spot-on. I hadn't realized that most cranks are designed for a "standard" chainline; On my HT double, it's 43.5mm I think, to the center between the two rings.