[Coleydog]

Instead of two surfaces for clamping, spacer will have four. All the bolts will be in shear either way but if any nick-burr-dirt is caught between those four surfaces you could have problems down the road. Torque to the proper number and check often. I personally used one for years till I got a spool, never a problem back then. Also it depends on what the application you have, steet-strip or just race. Biggest advantage of spool, bearing slips on and off for easy setup.
Hope this helps, Mike