Pat,
Seat comfort has several aspects.
The normal trade off of recumbent seats is between
"recumbent butt" and ergonomics. Many riders don't want
to be real laid back. It certainly does feel different.
is hard to look back and takes some getting used to.
With the "Barnett Williams" type of sling seat, you
run into the problem of the fabric hitting the back of
the thighs when you tilt the seat back past the
designed angle.
Many riders have reported good back results with a hard
shell seat. But, this requires a pretty extreme seat
angle, so that you are, in fact, lying on your back as
opposed to sitting on your bottom.
Mark Stonich, a recumbent builder and designer of some
experience, has stated (if I've remembered correctly)
that you need a seat back recline of 55 degrees from the
vertical or more to eliminate recumbent butt.
You also need the bottom bracket to be in a reasonable
position, after your back is comfortable, to be able to
develop some power.
Your Evox, IIRC, is a comfort bike of the new look. As
such, you are limited in how far you can recline your
seat. You will soon reach a point where you can't reach
the steering. Changing the steering will result in a lot
of tiller. You will be laid back to where you can't push
the pedals with any authority.
Recumbents really should be designed as a system. The
seat is only one part of the system.
While the bicycle seat industry is a multi million
dollar operation, it has long been my contention that
new riders buy seats and persevere in riding through the
discomfort. When their rear end stops hurting, they
think they have finally found "THE SEAT". It fact, they
have more probably trained to the point where they could
now ride comfortably on a sharpened fence post.