It is obviously not the S1 Low Direct Mount type you need because the bolt distance of your frame is 22.1 mm, while the S1 is used on frames with 42.7 mm bolt distance.
However, both the S2 and S3 types will fit a frame with 22.1 mm bolt distance. I am also going to put a SRAM Low Direct Mount FD on my 256 frame, but I am not sure if I shall use S2 or S3 type, or will both types fit if the 5 mm spacer on the bolts are either kept or removed?
If this is correct, what type should be used without the spacers, S2 or S3?