We haul a 10ft trailer for the quads behind our CH32BL and just fit within the overall length limits here in Alberta. That being said there seem to be few other Provinces / States that allow the triple tow.
We had a local fabrication shop cut off the factory bumper and install a heavier unit welded directly to the frame with a hitch integrated. It is rated for 3,00lbs so the weight is not an issue.
There is much discussion on this forum about voiding the frame warranty but it is a risk we were willing to take.
If you do go this route, remember that you will have no way of seeing the second trailer behind your FW while traveling down the road. There are back-up camera kits that could help or alternatively you could install some flags on the back of the boat trailer that hang out far enough that you can see them behind the FW. We went with the flag route on ours. Works fine. I recently bought a wireless back-up camera from a local dealer to give a better view of the quads on the trailer, but despite the claimed 300ft range, have not been able to get a strong enough signal in the truck to be of any use. My next step is to try a passive repeater to get the signal out of the trailer itself.
Good luck with whatever you do.
Bumper hitch for triple tow
2011 F350 6.7L SRW Lariat