as mentioned , the wiring on these bikes is 40+ yrs old. the very reason to use a relay. to remove any doubt that the ignition receives full voltage. preferably fused. in my opinion.
i originally connected mine via the green/white wire that supplies the flasher unit. nothing wrong with that if you are certain
of its connections. i removed all doubts for myself by creating a dedicated power source.
been using these ignitions for a good while now (2013), ( i have three) and cannot fault them .
Mentor to all self appointed (and genuine) GURUS.
An LTD is........it just is.