I am re-doing a bathroom and I am about to install a new steel tub (someone
else is doing the actual work, but it is easier to just write "I"). The
walls are ripped out down to the studs, and I will be using 1/2-inch cement
backer board where the ceramic tile tub surround will be going.

My question is about where the tub goes in relation to the cement backer
board and the wall studs. Around the 3 sides of the tub where the ceramic
tile tub surround will go, there is a 1-inch "tile flange" on the tub (
http://bootz.com/Downloads/Alohawholesale.pdf ).

Option 1): If I mount the tub up directly up against the studs, and then
apply 1/2-inch cement backer board from the top of the tile flange up, then
the cement backer board will be sticking out (from the wall) about 3/8-inch
past the approx. 1/8-inch thick tile flange. Then, if I bring the ceramic
tile down past the bottom edge of the backer board to close to the
horizontal top of the actual tub, there will be a gap of about 3/8-inch
behind the tile to the tile flange.

Is that how the install is typically done?

Option 2): Or, I could apply the 1/2-inch cement backer board to the studs
first, and have the backer board come down behind the 1-inch tile flange,
and then mount the tub up against the cement backer board instead of
directly on the studs. But, if I do that, when I go to do the ceramic tile,
the tile that goes over the 1-inch tile flange on the tub will be sticking
out due to the approx. 1/8-inch thick tile flange.

So, that doesn't seem like it would work.

Option 3): Pad out the studs about 3/8-inch; mount the tub against the
padded out studs; then bring the cement backer board down to the top of the
tile flange on the tub. That will leave the cement backer board about even
(flush) with the 1-inch tub tile flange. Then tile down past the top of the
tile flange to close to the horizontal top of the tub (which will leave no
space behind the tile where it overhangs the tile flange); and then just
caulk the gap between the bottom of the ceramic tile and the tub.

Can anyone tell me the "correct" way to do this? -- assuming that there is
one correct way. Is it Option 1, Option 2, or Option 3; or is there some
other way that is the correct way to do this?

Thanks.