We have a tub/shower combo in our master bath which we plan to replace with a walk in shower. On the bathroom forum, I was convinced that a Kohler cast iron shower base is better than tile pan unless I really trust the tile installer... and it looks like a good product. However there are 2 models available one is 60x30" and one is 60x32" our rough in area would allow for the larger size, and of course that would be preferable. Kohler recommends their offset drain version of the 32" Bellwether model for tub replacement.

However I measure the distance from our tub drain to the current finished wall and it is 9" to the plumbing wall and 14.5" to the long wall (so add a little to the roughin/studs). The Kohler 60 x 32" model with offset drain states that the drain is 14 1/8" from the long wall and only 6 1/2" from the plumbing wall, isn't that unusually close to the edge?

http://www.us.kohler.com/webassets/kpna/catalog/pdf/en/K-9166_spec.pdf

The non-offset drain model looks like it matches the dimension to the long wall, at 15.5" to the rough in edge. But the distance to the plumbing wall is still only 6.5".

The other model, the 60x30" Salient, is short in both dimensions.

So will they be able to install this base into our existing location with only minimal modification to the plumbing or would this require expensive extra work to move our drain over? This is a second story, wood subfloor.