The problem with putting rubber between the CF base and any of the
components that attach to it is that the bolts can never actually be
“tight”. They are just pulled down until the rubber is compressed.
This allows a little movement in the assembly and while it probably will
not cause a failure in this application, it is not ideal. If the rubber
is very thin, like a light duty bike tube, it will pretty much squeeze
down to nothing and not hurt anything. If it is thicker it can cause the
CF to try to deform around the hole into the rubber over time. This
tendency to “creep” is something to always keep in mind with plastics
and composite materials much more so than metals.
It is best to have all parts match up perfectly and have nothing between
them, and keep the bolts tight. In the real uni world, many components
do not match up perfectly and this may be the reason for the
recommendation. You can put the seat post/rail adapter against the seat
base and see if it contacts the surface well and not just in a few
spots, especially sharp corners. If you have the means to file or grind
off any sharp contact points, that is the best answer.

That’s my opinion on rubber, but I'm flexible.

Maybe someone else can give you a more helpful answer, like "yes" or
"no".

Scott


--
S_Wallis - MUni Motivated

"Don't neglect your knees! They're really useful." Words of wisdom from
Cyberbellum

"I am always doing that which I can not do, in order that I may learn
how to do it." Pablo Picasso
------------------------------------------------------------------------
S_Wallis's Profile: http://www.unicyclist.com/profile/1520
View this thread: http://www.unicyclist.com/thread/34204