Hi...i am a new user here.I think the strut support is more important than the case itself - as long as the mass is centered above the top plate, I wouldn't worry about the case as much as the rack.I've used padding to modestly even out the load and eliminate oscillations of the rack under load when going at highway speeds over bumps, but my Elcon 2500 ultimately wound up strapped to the passenger seat in a duffle bag or a pelican case because it was starting to strain my top rack and the OEM side rack over time.
Yes, I agree (and welcome!). The top rack needs reinforcement in order to handle 15lbs of load for any length of time, and the OEM side rack probably suffered from me putting an Elcon 2500 in a case repeatedly. At a minimum, it's worth stabilizing the top rack with padding between the tab and the tail plastics.
I did wind up putting my Elcon 2500 in a duffle bag and strapped that securely to the passenger seat and the top case to stabilize everything. I'd then open the duffle bag from the top and in front to pull out the charger, hook up the cables and use it. I tried a Pelican case, but it was difficult to find one large enough to enclose it well yet not interfere with a good riding posture.
FYI, the charger under discussion here is 7lbs for each modular 3.3kW unit, so it's easier to distribute the load, and that's 6.6kW per 15lbs instead of 2.5kW for the 15lb Elcon 2500.
The Happy Trails side rack for Zero is very sturdy and more ready to support a charger on each side. (Side Racks reference:
http://zeromanual.com/index.php/Zero_Aftermarket#Side_Rack)