Designing Kitchens and Bathrooms - Tub wall sealing

Installed a tub wall kit and have used polyseamseal kitchen and Bath Ultra between the walls and the tub ledge. This was a new wall kit with an existing tub. I scrapped (with razer blade) and thoughly cleaned (with alcohol) before installing the caulking betweeen the walls and tub ledge. I heated the room to 80deg to ensure curing and still the seal between the tub eventually starts to pull appart. If I press it down it will look sealed and not come back up until the next shower.I have re-caulked this twice, but still the same problem. First time the manufacture said the caulking I used was past it's shelf life. I am thinking after removing existing caulking I will sand the tub surface with 80 grit sandpaper and wipe with acetone. My question is will the tub walls be able to handle the acetone? Also what is recommended to use. I really think I should try another brand of caulking. I was thinking GE II 100 percent silicone. Any thoughts?
Thanks,
J

J, you mentioned all the correct steps except one. The area you will be joining must be completely dry. Setting fans in the shower area for at least 24 hours will help. Any moisture from behind will denigrate the effects of the sealant, even GE Silicone II. However, GE Silicone II is probably an ideal sealant for your situation. Remember, however, it is silicone, not water based, so apply it perfectly or it will look really bad. Another problem you may encounter is the looseness of the panel at the base. If it is not securely fastened, any movement will cause the seal to fail.

You speak of movement on the base. There is the green board a space 1/2" then the tub flange. The bottom 1 1/4" is not supported by the green board and only contacts the back flange of the tub and a bit of silicone behind the wall. So, there is the slight movement to the silicone behind the wall compressing to some degree. It's very slight, maybe 1/16 without the wall caulking in place. I don't see how this could be avoided or eliminated though.
Thanks,
J

Since you have movement, you'll be doing this often (probably even more than you would otherwise), have you checked into the strips that go along tubs? I found them at this link (http://www.lowes.com/lowes/lkn?action=productList&N=4294961544&Ne=4294967294&Ntk=i_products&Ntt=strip+caulk) for Lowe's. If you think you need it, you could get some of the "Caulk Saver", also to help fill in some of the space you were referring to.

I don't know how well the stuff works, but it's probably worth a try. Good luck! :)