This experiment with reviving an 81 Raleigh road frame has brought up a question. The frame angles on the bike are 74/74. The bike I moved the parts from (bike B) is 73 st/71 ht.
The fork on the Raleigh is 531. I don't know the offset.
The fork on the bike B is a Miyata cromo from an 85 912 with 45mm offset.

The ride quality between the two frames is significantly noticeable. The Raleigh has a harsher ride, especially on poor road surfaces. When I designed bike B it was purposeful as I wanted straight line stability (country roads don't have many sharp 90 degree turns). One added benefit with this has been a Cadillac like ride quality.
The question I have is three fold. 1) Does the head angle really make that much of a difference? 2) Does trail affect ride quality in terms of harshness? 3) Does head angle have an affect on harshness because it lays the fork out flatter which in turns provides more "suspension" or movement of the blades on rough surfaces?