If it were me, I would probably use wider gussets or even full length
strips of plywood, just for the added strength.

The thing is, you don't really NEED all that much strength. You're
only holding up the bottom chord, fiber insulation, and sheetrock,
That's something like 7 PSF dead-load. The only problems occur
in 6 years, when someone decides to hang a swing-chair from
the rafters with lag-bolts...