I installed a standard fuel sump drain under the fuselage and connected it to the gascolator.  Very convenient for draining during preflight inspection.  I have attached a photo.  It was very simple and only involved a couple of fittings and an Aeroquip hose.  Parts were available at local  race car shop.  Of course, the sump drain came from an aircraft supply store.
 
I assumed when you said extension you were referring to a drain.  If not, I misunderstood the post and you should ignore all the above.  :)
 
Jim
98AF Angels Playmate