hmm yea i did notice that thats why i have not yet cut it... in that picture you have above that is a ke70 tank did you say? should i be keeping the internal tongue in the ae86 tank? the way i have done it is to cut the ae86 filler neck off quite low, as low as the pic above, but leaving the internal tongue sticking out so that it will slide up inside the ae71 filler neck, which ive let intact and bolted to the car, and the rubber piece attached to it. then we lifted the tank, slid the tongue inside the still-mounted ae71 filler neck right up to the little lip/edge on the ae86 stub (on the tank)...
does that make sense?