[Peterbug]

dab1950 pointed to the reduced weight rating on your hitch when using the hitch extender. The reason why is important for other adjustments and modifications you may consider in the future: The extension from your hitch receiver works like a lever or 'cheater bar', increasing the rotation force on the receiver.
This is very important for those towing without a WDH, and the temptation to find some manufacturer that does not specify the derating of the hitch capacity is to be resisted.
A WDH does reduce this rotation force IF THE WDH CHAINS ARE TAUT, but does NOT if the chains are slack as might happen when the front of the TV goes down. So, as the TV and trailer go over the peak of a hill, the chains go slack and do not protect the hitch receiver.
With all of the heavy loads, complexities of dynamic forces, and legal liabilities that would result from such a modification, my suggestion is that you spend your time modifying the canoe mount so that you can easily slide the canoe forward while parked and TM is up. Tip: Make a yellow reminder flag that you clip to the canoe in front of your windshield to remind you about the canoe's forward position, so that you remember to re-set the canoe before getting back on the road.