There is some miss conception on your part Geof.
There are no "cracking" issues on 5th wheel HITCHS -- There are frame cracking issues on the nose of 5th wheels pulled by mdt's. So far -- I've heard of none when using a converted class 8.
an air hitch for a bumper pull -- no such animal.
If your desire is using a class 8 for a bumper pull trailer -- It's imperative to convert it to a 2 axle Tractor -- It's essential to eliminate 2 of the 4 air bags -- and loosing one driver is advantagious. In your example -- it's manditory to soften-up the rear air suspension as much as possible.
The way I'd approach this (frankly -- I'd not deviate from a 5th wheel or goose neck trailer) would be to convert to a 2 axle Tractor and shorten-up the frame as close to the airbags as possible. Then get a LARGE old compressor tank and mount it to the frame. There is a balance airline connecting both air bags together. Remove it. Buy perhaps 10 3/8" quick air line t's and a roll(50') of 3/8" air line (I'm trying to remember on mine if it's 3/8"s or not -- but .. you will get the idea). Install 2" of airline in one bag -- then a "t" then 2" of air line and another "t" ...... and so on till you get to the other bag.
Drill and tap the air tank for 10 fittings and make 10 "runs" of the 3/8's air line from all the "t's" to the tank.
In doing this -- you are greatly increasing the "volume" of the air bags. Being that air is compressed in the bags -- and the increased capacity with the addition of the air tank -- this will soften up the rear of the tractor. If this Illustration softens up the rear to the point that the frame steel stops hit the rear axle housing -- simply remove one "t" between the bags (quick connect air fittings are a snap to work with-no tools required).
In this example -- the whole exercise is to soften up the rear suspension and locate the receiver as close to the rear axle as possible.
As I see what your intentions are -- you may have a trailer with a tongue weight about 2000 pounds. Simply get the largest coupler and ball offered -- and it should work -- if your mind is set on a bumper pull -- again .. .. go to the race track in your area -- and you'll see most racers use the goose neck trailers -- some use the 5th wheel method -- I can't remember anyone using a bumper pull behind anything but a pickup -- Although I do seem to recall someone using a trailer with a pintle hook setup -- but rare.
Instead of re-inventing the wheel ....... go to the track and "look" -- and if your like me ....... take pictures (I forget a lot !!).
Be interested to see what others may have to offer .........
Tootles ......
OLDphoneman
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