[Nonfractal]

RE: The body post topic.
Ebay search, use the phrase "spoke tubes" 

Here is a link to one supplier 
https://www.ebay.co.uk/itm/12-White-Bike...ect=mobile

To loosen the screw grip, drill to size.

To make the tubes tighter (and prettier) on the screw, use a slip over shrink wrap tube (usually used for power cable joints) and use a soldering iron to shrink to size. (Don't use a hair dryer, that would warp the body) 

Some old-school constructors use side mounts (as do "slot.it" on the hrs2 chassis) but this does not provide controlled rocking of the body around a fixed pivot point that can be achieved with body posts.

The modern way it to have 2 posts, 1 front, 1 rear , both on the centreline, and float the body on 4 set screws , 1 at each corner of the chassis. 
Refer to Black Arrow cars for a perfect execution of this concept.

Alan