reinforcing trailer tongue

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I need to reinforce a trailer tongue on a trailer. it is a 28ft flatbed and the tongue is 3x5x.25 angle iron. the perimeter of the main deck is 5x6.7 C Channel, I have no clue why the manufacturer made the tongue out of angle iron, but they did and so I'm here. I was planning on getting another piece of 3x5x.25 angle and welding it to the existing angle to box it, then add some gussets at the point the tongue meets the bed. The other issue is that they made the tongue very deep under the bed and the axles are set back- think more like a boat trailer than a flatbed, but this was a commercial flatbed made by a company called Ennis, about 20 years ago or so. As a result there's a lot or torsional flex that can be imparted to the bed, and I think by boxing the tongue  about 3/4 of the way back under the frame, it should reinforce the tongue section and stiffen the trailer at the same time.Sound like a plan? Am I better off getting some 3x3 thick wall tube to run inside the existing channel, or a use a 3x3 angle to box in the 3x5 so I'm welding in the web rather than at the edge of the vertical member? I've been trying to run span calculations and figure what the best option is, but I'm way out of my league in the math and trying to figure out the dynamic loading over the length of the beam while still approximating the point loading at the connection point to the bed of the trailer where dynamic down force will be strongest, so any ideas would be of great help. I'm working on moving so all my gear is already 2k miles away, I have a friend with a shop that is letting me use his Lincoln 180 Mig to stitch all this together so I can get it loaded up and on the road, so while I'm not a professional welder I am NOT a shade tree running a 90amp from HF expecting it to weld structural steel in one pass.

Trailer is a double axle 28ft 12k. I will have a 2006 Suburban 2500 on the back over the axles and a thousand or two lbs of housewares, etc, in front of that, so it will be close to capacity but still under 12k gross. Towing with a 96 F350 dually with a round bar WD hitch. Thanks!
Reply:Has the tongue failed over the 20 years the trailer has been used? Flexing is a good thing, I wouldn't suggest changing anything unless there's been a problem.Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power

) Hobart MIG
Reply:that is a good point. My concern is tongue weight with the long bed in front of the axles. The PO used the trailer for transporting his tractor- he would use the front end loader to place the attachments for it on the front of the deck, then load the heavy tractor itself from the rear onto the deck over the axles. I'm just worried I'll have too much tongue weight and damage the tongue, being angle iron. My other concern is that for some reason the mfg installed 2 flip down tube mount jacks, one on either side of the tongue instead of a single jack. Someone stole one of the jacks off one side and the PO didn't replace it, so he would use one side to hold the trailer up, which caused the vertical wall of the angle iron to bow out slightly under the mounting point on that side, so I'm concerned that damaged the integrity and needs some reinforcement at least. I didn't see it before I bought the trailer, unfortunately. I cut off the mounting tubes from the tongue and welded on a single 10k drop leg jack in the center of the tongue.I'll get some pics to put up tomorrow when there's daylight of what I'm working with. My friend with the welding shop who is letting me use his gear makes trailers built very well with thick wall tube tongues so he suggests to box in the tongue at the least for strength, so I started looking at options and trying to figure out myself what material would be best, so I figured it wouldn't hurt to get further input from the knowledge base here.
Reply:I just ran outside to take some pics of what I'm working with. You can see in the one pic from the under side of the tongue rail what I mean about it being bent out slightly where the jack was mounted.https://ibb.co/m4cd95Phttps://ibb.co/dbh8fPvhttps://ibb.co/4jQqJHg