Basically, 16.5" rims (or any other xx.5" rims for that matter, ie 19.5, 22.5, 24.5) are for commercial/heavy duty service. They're designed to run tires that can handle high pressures (80 - 110 psi) and were never designed to be used with pressures under 30 psi, which is why they lack the safety bead. You typically only see 16.5" wheels in 8 bolt application, too.
16.5"s would be fine if you converted them to use beadlocks but why? Use 16s or 17s instead, more options out there. The one major advantage, though, is that they're easier to work with when seating/unseating them. LR
'09 Ford Ranger FX4 that gets abused a lot... but doesn't like to swim though.