I had three bonded boys (single bun paired up, then a third added) who were easier to bond than my male/female pairing :lol: They were living together literally within a few hours of meeting, snuggled up within a day I think!
I think the potential for single buns and injuries would apply to bonding any combination in a trio, or even a pair. However, it varies from bun to bun, and even if 99.9% of male trio bondings worked out (not saying they do, just as an example) it's not going to guarantee that yours will (or won't)
I think you need to weigh up the pros and cons for the buns - e.g. if it's just that a trio would make things easier, or is it really not viable to just get a female bun for company for the lone boy? The potential for injuries when it's more a convenience thing probably wouldn't be worth it in my opinion, but if it's the only chance he'll have at company then I'd probably be more inclined to try it.
I would, however, take precautions and time it well - e.g. don't do it just after vet closing hours or on a day they're not open if you're not prepared to pay emergency vet fees, try to ensure you've got transport to a vet (access to a car and someone who drives if you don't), do it on a day you know you can spend all day supervising and can stay up late overnight to keep an eye on them etc