The amount a TC drops behind the rear bumper of the truck that's hauling it varies considerably from one TC to another, and from one truck to another. I wouldn't just assume that because one person was successful with a lengthened tongue that it is the "right way" for everyone.
Lengthening the tongue wouldn't work with my TC at all, no way. There WOULD be contact between the tongue and the campers bumper, I gar-on-tee. I've used a homemade 48" extension off and on for 30 years without a single issue. Truthfully though, if I needed to do much towing with the TC these days, I'd buy a SuperTruss. They are light years ahead of the extension I made.
There is nothing at all wrong with using a hitch extension to tow with as long as the TC is on the truck. The weight of the TC mitigates the negative effects of extending the hitch. Try towing with an extended hitch WITHOUT the TC on the truck and you will very quickly learn the meaning of "leverage" when you take your first sharp curve.
:):)
