Using a Wayne Hicks suggestion make a ply mockup of the left armrest top, accurate width forward and aft and straight betwixt, and profile the outboard edge by taping on small bits of cardboard. Use this to cut out the foam.
Trimmed all yesterdays bits and they look good. Absolute bitch getting all the peel ply off the conduit conduit.
To avoid thinking too hard about installation, and while the method was fresh in my mind, made another set for the right side in the same fashion.
Installed Rudder conduit conduit with urethane bond, clamped with cleco.
Making a template
Resulting foam looks good, but I am deeply suspicious...