I almost swallowed my gum when you said you wanted a tub that is 54" deep!! Actually, that tub is 54" LONG, 30" wide and and only 19 inches deep. Is there any way you can find enough room to stretch your space to a 60" model? You'd have many more choices there...

As for the surround, I am no expert but 1½ inches per side doesn't seem like enough.
Susan ~

Sorry, I guess it would have been more correct to say 54" long, DEEP tub! I don't have a specific depth in mind but since it's a shorter than average tub (and no, I can't find the extra inches for a 60 inch model unless I turn the tub the other way, which I would rather not do), I would like it to be deep-ish for soaking purposes.

Can anyone answer the question about using a drop-in tub as an occasional use shower? I'd totally appreciate it.

I am also getting a drop in soaking tub and using it as a shower. It does not come with a tile flange. I called the manufacterer, Porcher, and they said I could purchase a universal tile flange kit. I am not a pro so maybe someone else will add something.
Donna

A universal tiling kit is a strip that the installer glues to the tub so that there is a vertical surface behind the bottom of your wall. You bring the walls down over it. Some contractors like it; some don't. It's used a lot in my area and I've never had anyone complain about it.
As for the mounting area for a drop-in, you can usually come straight down at the edges. You only need that extra lip around the tub if you want a place to set stuff, or you like the look of a platform around your tub--but you might want to try to get a look at the installation instructions for the tub you are interested in, before you order it.