How many cosigners for joint bachelors and house hacking?

[Paul R.]

I'm working on my first go-around of tenant screens for a house hacking arrangement.  The potential tenants are aware that I'm the PM and neighbor.

Rent: $1,600

Tenant 1: a few years about of school, excellent previous landlord references, two jobs, seemed clean cut and put together, Gross Income to half / full rent: 6.77x Half Rent / 3.3x Full Rent

Volunteered dad (well qualified cosigner) who agreed to be cosigner and passed all screens.

Tenant 2: Similar life status and feel as Tenant 1, lives with parents (no rental history), toured apartment with his mom, Gross Income to half / full rent - 3.6x Half Rent / 1.83x Full Rent.

Would you require a cosigner for tenant 2 or is tenant 1's dad enough when combined with both incomes? I work in the "what if" industry, so naturally the "what if" in a friends fight comes up.

Everything else checks out on both (strong credit, no evictions, no criminal, etc.).