I have a tea for two soaking tub, not whirlpool in the 5.5' size. my thoughts in no particular order 1) have you sat/seen the 5' size? I remember a NYTimes story about renovating a brownstone that commented that they got the 5' tea for two, had to downsize from teh 5.5 and were unhappy b/c it killed the depth along with the length. 2) the drain set up absolutely sucks. I had 2 plumbers and my father in law who is a handy man screw with it, none could get it to reliabily work, it either didn't drain and held water or, drained, but wouldn't hold water. We resorted to removing the drain and using a rubber stopper. 3) we were acting as GCs on teh renovation..... we were buying the fixtures and having a plumber install... however, he wasn't any kind of set up to get this up to the second floor master, nor manuver it around... we did that. it weighs about 450lbs + we decided that undermounting would make sense. on top of that, I bought mine off of craigslist for a really really good deal. the downside, one corner had a small chip. it could have been touched up, but I used the "savings" to undermount with granite. It really looks sweet. I'm really not sure what you're doing with sliding glass doors? as far as I can tell they don't have set up that would accomodate a shower, so I'm nto sure doors would be needed... I like the tub, but we don't use it much, we should, but don't. if I were to do the whole bath over again, I would have done a larger shoewr and skipped the tub.

Another thing to consider regarding your layout considerations is going to an under-mounted tub. I was looking at 60 inch tubs to get a little more decking space and ended up going with a 72 inch tub that when it is under-mounted will give me about the same deck space as the 60 as there is 5 inches of flange all the way around the 72" tub (10 inches off of left to right and front to back, rectangular tub). I get the interior space of the big tub with the footprint of the smaller one. I will also say a little prayer to my favorite wrench to send a master plumber your way. All of us DIYers need all the help we can get.

"Pain" was not a good choice of words. Drop-in relies on solid, level carpentry (deck and frame), so as long as that's good and the drain is put in the right place, there should not be an issue. Somebody has to do the framing properly. Alcove tubs can be tough sometimes, such as when there's a foam base and the floor underneath isn't perfectly level. Then it can creak when you stand in it unless they foam it and shim it, install the stringer, etc, just right. Lots of trial and error sometimes. Dealing with this comes with the territory. Free-standing tubs are another thing altogether, since they just rest on the level, finished floor, then get hooked up. Just choose what you want, then find the right guy to do it. I think you are right about not seeing the apron of an alcove tub. I did a bathroom recently that did use an alcove tub with apron, and that was the biggest regret of the client. But we did not have the depth for a drop in, so it had to be that way. You, on the other hand, presumably have the luxury to do what you want. Go for it.

To all responders - many thanks for the comments and suggestions. Was able to open access door at plumbing end of tub and was able to see steel mesh and clumps of plaster below tub rim on exterior wall but no sign of studs - so I assume that plaster with mesh support is also behind wall tiles. This would explain erratic readings with stud finder. Exterior wall is brick - not sure if stud finder will give reliable readings through brick but will give it a try. If so will give me some general idea where studs might be.