Here's how I do it.....
Green is your bearings.
Blue is a washer that prevents the collar from rubbing
on the outer bearing race.
Bearing blocks can be what you showed, or aluminum/plastic/wood blocks
with the bearing fixed into them.
The clamp collars prevent any end to end movement of the screw and also
allow for extra extended length for the coupling.
They also don't cause need for a flat on the screw or use set screws that will
damage threads....and destroy any plastic nut that's installed or removed.