Weddingbee boards

This is my dress (FYI, the model and I are nearly identical in size, proportion, and coloring):

This is my problem:

1. It's very sheer, despite being fully lined, so it seems that I'm going to need to wear a full slip of some sort.

2. Slips tend to have straps. Although my dress has straps, they're thin and don't widen to connect to the body of the dress, so even something like this Spanx slip with thin straps will probably peek through. And anyway, it's not full-length.

3. There's this Spanx slip, but I've read some other bees' posts, and it sounds like it will probably smash my poor little 32-B-and-a-half cups into oblivion. I don't want to look like a 12-year-old boy on my wedding day! (But maybe I could wear a strapless push-up underneath the Spanx? Would that be a terrible idea? I've never worn Spanx, so I have no experience with how it works.)

4. I thought about this VS catsuit (+ some sort of bra), but a) I think the straps would show since they're kind of wide, and b) since it has leggings, not a skirt, I'm pretty sure my dress would go right between my legs and make itself comfortable there.

5. There's always good ol' DB, with a full-length, strapless slip, but I'm not convinced it will really do me any good... or, for that matter, even stay up.

6. I am planning to add a decorative sash to my dress, so maybe, just maybe, I could pull off a bustier, lightly tack the straps to the gown's straps (!!), and wear a skirt-only slip from the waist down? This would only work if the sash (i.e. my normal waistline) were exactly where the bustier and skirt-slip met.

7. I could go commando or wear a laser-cut nude thong and go the band-aids route. (Eek!)

8. Or I could just get a new dress. A new, very structured, very well lined dress... =(

Bees, any ideas? Have you had a similar experience? What was your solution?

I'm not really worried about the straps slipping--I would either have my mom put a small tack in to keep the straps together, or I'd use fashion tape. I'm more worried that, because the straps on the dress are thin and just kind of attach to the bodice, whereas most slips' straps kind of widen out into an extension of the cup, the slip (specifically, the part of the slip where the cup is becoming the strap) will actually peek out from underneath the dress; I tried the dress on with a pretty normal bra, and it peeked out quite a bit. (This is really hard to try to explain!)

I know that I should really just try these things on under the dress, but they're all so expensive, and I'm really reluctant to order five different undergarment ensembles just to try on! And, of course, pretty much none of it is available in stores where I live.

@aunt pol: The thought had crossed my mind, and it may be one of my best options. I'm worried that it might cost too much, though--I don't want to pay more for alterations than I did for the dress!