Hi!
Please don't even try - it is a surefire recipe for disaster!
Boars should be best kept in pairs. You can end up with four singles that won't go back together at the worst when the stress of the meeting is causing the leaders to turn on their partners. We have been contacted by new members over that issue several times before; and certainly rather regularly over fighting issues in quartets.
Boar quartets have a near total fail rate unless you have very different disabled/carer companion dynamics, LOTS of space (like half a fair sized room so the boys can live well away from each other to not be forced to fight over encroachment) or you have pensioners whose testosterone has all fizzled out (five years plus) and who value company over status.
I can still count the number of successful boar quartets I have verifiable knowledge of on one hand even after a decade on this and other guinea pig forums!
More information in these links here:
Adding More Guinea Pigs Or Merging Pairs – What Works And What Not?
A Comprehensive Guide to Guinea Pig Boars
Please don't risk the stability of the pairs just for your own gratification. Boars work either in pairs or in large herds with oodles of space, but trios and quartets are by far the most instable combinations with an extremely high or near total fail rate.