My intuition would be: up to 128 bit/16 bytes always pass by-copy. For larger structs up to about 1024 bytes start with pass by-copy and switch to by-borrow onl

My intuition would be: up to 128 bit/16 bytes always pass by-copy. For larger structs up to about 1024 bytes start with pass by-copy and switch to by-borrow only if you profiled and found a performance bottleneck.