Nope, you can use only two. I sell the rest for the resources.
Just in case you're unaware of this: you no longer lose units if your rum drops to zero with negative production, so - with some raiding and quick spending - you don't really need those relics. I have two and haven't been using them since the troops stopped caring about zero rum. My production is at about -115k/h.This is from my account:
Except when the raids return, I'm at zero. Haven't lost a single unit to the rum negative.
And here is the official announcement from about a year and a half ago.
The only "downside" to big negatives is that when you drop below -100k rum per hour, you can no longer boost production of units.