I am using 3.5" dia Aeroduct-CAT ducting for a short distance directly
from my intake plenum under my fuselage to the carburetor. The problem
with the CAT is that the wire reinforcing and fabric do not give
radially well, so it transmits some engine vibration to the fuselage.

I would like to find some very flexible ducting (3.5 " bore). I noticed
some of the production built flexible rubber ducting in my car from air
filter to the fuel control(?). I was looking at my 2.5" rubber hose
that ducts the exhaust fumes out of the garage but it is really bulky
and not easy to apply a clamp to.

Anybody has specific product and sources suggestions?