I recently switched from a pickup camper to a 5th wheel type of trailer.
I don't want to put the 16 foot canoe on the roof of the brand new
trailer, for one thing there are no good attachment points.

These links show a canoe mounted above the cab of the truck, extending
over the front of the truck. You can't move the canoe back without
hitting the 5th wheel trailer.

http://www.canoeleg.com/5thwheel.htm

http://www.motorhomemagazine.com/for...g/15636776.cfm

I measured the distance between the back of the truck cab and the front
bumper as 12 feet. That seems like too far apart to have the racks
holding the canoe. I am not enthused about having my canoe racks two
feet from the end of the canoe. My truck is a 2000 Ford F350 with the
extended cab.

Alternately, I could go with a roof rack on the truck cab and a front
bumper mount, which would get the racks closer together, but perhaps
move the canoe too far forward. I think that I would be legal having
the front of the canoe four feet past the front bumper, but no more.

Apparently there are available commercial racks to do this, but I am not
necessarily adverse to firing up the welder and making a rack.

So how far apart is too far in terms of racking a canoe? At the moment
I have a 16 foot canoe, but I could go shorter or longer in the future,
you can never have too many boats.

Richard