Dual J-Head Kossel Magnet Upgrade

This is an upgrade to a 20x20 framed deltabot printer that is using wheeled rail-runners.
3 upgrades in one.

A: it adds a 4th wheel to the runners, making them much more sturdy.
B: it uses 12mm magnets in place of the usual rose-joints.
C: it can take 2 j-head extruders

It has a dual object-fan shroud, that runs from a single over-head 40mm fan.

extruders are 26mm offset tip to tip and 13mm from center on X

It has built in 30mm fan mount-point for hot-end cooling.

This design