Originally Posted by Yeti AS3

The narrow to wide blocks has to have another effect due to the pivot point. I ran the narrow caster blocks up front with RB5 axles/clamp hexes and found no loss of steering but much smoother and predictable steering. Width was about the same, but the pivot changes. On-road guys have done similar changes.
You could try narrow blocks with SC-R 3 line axles and shim 1mm to the inside to be equal to wide blocks. Use 1.5mm inside for for a little less rotation or stock axles for max rear grip. I found that 2mm inside on SC-R axles makes the axles rub on the outdrive at full compression. Just another tuning option.