I played around with spacers for a while. The tappered four hole still get's my vote, and it will stay on my setup.
I tried this gimmick four hole once, great for off the line torque and it even cured a few cruising issues too. It also helped with MPG. This spacer would be great for your car show cruiser that never see's above 3k rpm going from the garage to the cruise in. It made the higher rpm fall flat, and it lost some ***.
I even double stacked a 1" four hole on top of a 1" open on a RPM Air-Gap. It worked fine, felt like it really picked up the acceleration above 3500rpm
But, so far the tapered spacer flowed into the dual plane in my previous post is providing the best results. It even feels faster on the street than the big runner single plane I ran for almost a year.