I mounted two of the traxide relays to a thin metal plate.
The thin metal plate was attached to a left hand side bracket that connects the left wing to the body. Its quite near the heater blower plastic intake.
Sorry no pictures.
Could you get 3 traxide size relays on that plate? Probably just, a piggy pack solution might work better.
I preferred in bay rather than behind the headlight because 1. easier to get at, 2. a bit higher.
If you really need a pic to explain where I stuck it let me know and I'll take one.

