I have a similar issue on an ultegra bsa bb. If I don’t use spacers on DS it spins ok with preload spacer taking up the slack, but the chain ends up too close to the inside side of the FD cage. If I put a spacer or 2 on DS then chain is in a good place but the bearings seem to bind up and it doesn’t spin very well. I think it’s because the DS crank can’t reach end of splines when spacers are installed and torqing it up just makes it tight against the BB. Gave up and put ultegra back on for now

Exactly the same issue I was trying to resolve yesterday. My main reason for tinkering was to try to eliminate intermittent outboard chain drops with an Ultegra 12sp FD w/Pass Quest chainrings & Xcadey PM on a Speeder SC-R55.

The FD's limit is maxed out and still tries to push the chain too far at least once or twice a ride, which is significantly more than I feel is acceptable. 3mm & 2mm - shifts on point, but completely binds up at torque. 1mm DS torques down properly with the ability to adjust preload, but it's then back to the same issue. Having said that, in the bike stand, you can bang the chain up and down no worries, and only around 1-2 times will the chain either drop or ride the teeth before popping into gear. Take it out on the road and it's roulette. For the most part, it's been fine, and the chain will jump back on after a few pedal strokes. However, it's not without a few cursory scratches to the cranks.

I've not got around to trying it yet, but my next port of call will be to try to remove the preload from the equation and attempt to use spacers to load and shift the crankset over into a decent chainline. Wonky Q factor or not, I'd rather not have the chain keep dropping mid-ride.