So im going to use the normal cargo extension that clamps onto heaset tube at low level and extends to front wheels but i will use either m12 or m10 as from experience the m8 isnt strong enough and sometimes throws the front wheel off to the opposite side of the connecting rod which is annoying.
and it will possibly have some sort of recumbant steerer for the other fork, and no the bed will be ridgid but as i said im looking at recumbent style mounting and this could be an option and also a possibilty of adding suspension either forks or recumbent style for the wheel fixing

If the above website also stock headset tubes in 3 or 5mm ill opt for recumbent style but will possibly add supports either side but not in a fork manner, obviously once the initial bed is built i can move forward from there as id need to see certain things infront of me to solve the problem
also without certain sizes of headset etc as they come in different sizes im unable to really draw it up accurately to get a better look at how it performs in terms of steering and movement

I will get the bed built up for now and then once i get a response from the above website i will then ask about the headtube or headset

Also the fixing point for the headset will be either on a fixed piece of box section with tube on the inside for the headet thats welded to the underside of the frame to allow for headset to be mounted without tampering with above rack ie keeping the bed level
or it will be recumbent as in drop outs from the frame for wheel mounting etc