Why so critical of "universal" flex radiator hoses?

Well to get the flow back, you could upsize the "flexible hose" about .5 to .7 inch. Then you might have proper flow in the relatively turbulence-free center of the hose. Then you could get a muffler shop to bend you up a proper hose router, and slide that fat boy in there. And finally, you could rework the spigots, to accept that monster.
Of course you would have to remember to never let a Mopar guy see what you did.
Alternatively, you could wire the secondaries shut and reset the rev-limiter to about 2800, and then to never drive it south of the 49/50th parallel, in the summer time.