Friction, fit and powder removal are the three factors in play with axle design for SLS manufacturing. Manage friction by applying 1-2mm rails on the static ‘not stressed’ side of the assembly. Keep the clearance between the rails axle tube at 0.3mm. In regions away from the rails, a clearance of 2mm+ will enable complete and easy powder removal by blowing compressed air through the powder removal access ports modeled into the static side.
Comment: Hybridisation is a new era for aerospace
Regeneration during braking would be a good start. Some wind-milling during decent could possibly contribute. Also the engines could be lower-powered...