Buddy has a very similar set up on his new 5'er, rated at 500lbs capacity, so the 50 will be well under that. But he still took it to a buddy's fab shop and ran channel 8' up the main frame and capped it under the bumper for additional support since he also double tows his heavy duck boat and just wanted piece of mind.
So completely doable, but obviously smarter to err on the overkill side when bracing it up because of the multiplied forces of the up and down it will get being towed and going over dips/bumps on the road.
I recently installed a hitch on my 5th wheel to drag my Jon boat, tounge weight isn't much so just tied into the existing frame back there and fully welded the drop down extensons vs the stitch welds from factory. I wouldn't tow my 20' trailer with 4 quads on it behind the 5th wheel trailer, but it's fine for what it's intended purpose is.
Have fun, more tinkering to fit bracing than anything.
2014 Sportsman 550 named "Chapter 7"
Lots of mods and add ons