J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Flexible shaft couplings

How many have installed a flexible shaft coupling? And did it make any difference.?
We are replacing our prop shaft and considering a shorter shaft by 1.25in to accommodate a flex coupling..(R&D Marine 910-002)..hoping to reduce vibration from the old Yanmar. Will also be replacing the cutlass bearing.