vent for tub

I have a strange configuration I would like to know if it will work to vewnt my tub, and also to act as a vent for my shower which is on the same 3" waste line 3 feet away. The pic is primitive but I hope i gets the point across. I would like to vent verticle off the 1 1/2 drain line between the p trap and the waste line. Drawing shows best.

Is this an OK setup?

You need a trap for the shower, vented.
And you need a trap for the tub, vented.
The two vents can tie together 6" above the top of the tub.

Though most plumbers do it at 42"

Thanks, in the diagram, will the vent that comes off the tub as shown suffice for the tub vent? I then can do a similar vent a few inches off the shower and tie both together at 42"