I'd say get yourself some
problem solvers decksters. I just got a pair, but haven't tried them out yet. Basically they're platforms that clip in to your spd pedal to make it like an A530 or whatever for when you want to ride with normal shoes, but then you just take it off when you don't want it on there and it's just your normal M520 or whatever you're using with clipless on both sides.

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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"