You should be able to do the whole sublingual administration with temazepam, same as any other benzo. I think the idea with subbing benzos is that while you don't fully absorb all of the drug in your mouth, the rest of the drug will be taken up in the GI tract, so you don't really have to worry about wasting any of it. Although temazepam has low water solubility, it may absorb slightly better under the tongue than in other mucosal tissue due to using saliva as the delivery medium (although I'm not entirely sure about that, its just some scientific wild-assed guessing on my part).
And Jah, as far as Temazepam dosages go, 15-30 mg gets me pretty well. I think it takes quite a bit of Temazepam for you to get a buzz because, unless I am mistaken, you are a pretty frequent user of benzos, for both recreational and medicinal usages...and off course benzos have high (if not complete) cross-tolerance, so its probably your high benzo tolerance in general that makes you require more temazepam to feel anything, it has nothing to do with any unique qualities of temazepam.
Be careful mixing all the benzos with that subutex though, man. I know that you know what you are doing, and that buprenorphine isn't the most powerful opiate, but I'm just trying to look out for you since mixing downers can sometimes end badly.
EDIT: Dangit, lefty beat me to all of this and said it in a much more coherent and less meandering fashion than I. C'est la vie!