Dolly trailer build question

[kenlms]

Hi all,

I am embarking on my first custom truck project and am building a dolly. I have knocked one up from parts of the Tamiya pole trailer and and other spare bits.

I have 2 what I think are important configuration questions:

1) where should the kingpin sit in relation to the axles? I copied the configuration from a truck kit, which has the king pin just behind the centre of the axle group, but it seem to sit tail heavy on the suspension under load.

2) Should the draw-bar be rigid mounted or pivot where it attaches to the trailer? I.e. should there be any vertical load transferred to the tow hitch?

Thank you for any advice!

Ken