Harry, before you go to welding you should check the GVW and GCWR of your MH and the weight of whatever trailer and "stuff" you might be considering. Frankly, if the answers don't jive I would not proceed any further.
Similarly, what will the overall combined length be, i.e. MH plus trailer, plus the trailer hitch.
Assuming you get through both of these steps I'll tell you what I do with a 40' pusher and a 20' trailer with a 5' hitch. All of these lengths are rounded and I actually come in at 64'8" overall length. My trailer when loaded with car and other "stuff" comes in at 9300 odd pounds and the difference between my GVW and GCWR is 10,000# and the manufacturer's hitch on the MH is also 10,000#.
Being a 20' trailer it has two axles each with electric brakes and the MH has a Prodigy brake controller wired in. Since this trailer was built for me I spec'd. 6,000# axles vs. the more normal 3500# or 5000# ones. Getting the greater capacity axles also allowed me to get 10 ply 16" tires vs. the standard 8 ply 15" tires. Likewise a 36" or 48" hitch is generally considered standard and I upgraded to 60" to give me added "kiss" protection between the rear of the MH and the front of trailer. The longer hitch also makes backing up without jacknifing a little easier. The 60" hitch also is constructed with 3 "I" beams vs. 2 on the shorter hitches. I also spec'd. the floor to be 3/4" on 12" center as some brands come through with 5/8" on 16" centers.
Did I go overboard- maybe, maybe not. Once I had decided on the length that I wanted these upgrades and a few other creature features caused the price to increase about $2400- which over the long haul I did not consider earth shaking.
We have towed this trialer for the last 16 months some 20-24,000 miles and have no regrets. Pre trailer we towed 4 down for 4 and 1/2 years and I doubt that that will ever be part of our style in the future. If you have any furter questions let me know, Ken, '04 DSDP...