On my older narrow Morgans I used Rutherford rear conversions and Spax shock absorbers.
The general consensus today is that Rutherford AVO's and Konis are better.
The Spax however transformed the ride and handling from the lever Armstongs.
Gomog do a test on the damping rates of various shock absorbers to compare.
For the +4 4seater I tried AVO's and found that Suplex front and rear with the Bilsteins to give a better ride. The problem was that I had weak rear springs on the +4 so perhaps not a fair comparison. The Suplex springs come with specially rated Bilsteins but they are not adjustable.
