Not completely understanding you need or wants, I may be off base with this suggestion. If so, I ask forgiveness.
For good acoustics, it is not considered advisable to have any speaker all the way inside a cabinet. Even bookshelf speakers should be brought right to the edge of the shelf, and if possible extend an inch or so beyond. This is to minimize the influence of the shelf itself on the acoustic character of the speaker. It's called "boundry effect." You may have noticed that speaker stands all have a top plate that is actually smaller than the footprint of the speaker itself to eliminate boundry effect.
My current center channel extends, at it's bottom edge, a full 2 inches beyond the shelf on which it sits. And being tilted up, it extends a good half inch beyond the shelf above the speaker on which sits my HDTV.
Were you to have the VP150 on it's back, so that the drivers were angled up slightly, and inserted completely into the cabinet, there would definitely be a reflection off the shelf above the speaker to the detriment of the speaker's sound. With only an eighth of inch difference between your cabinet space and the height of the speaker, with the VP150 on it's back, you could fit the vast majority of the speaker into the cabinet, right up to the point where that eighth of an inch stops you, and have the remainder extend past the shelves above and below.
I know that if the cabinet has doors you wish to close, or if you, or your wife, would find that configuration offensive, this option would be unacceptable. But, I just wanted you to know that acoustically, it is actually preferable.
Here is #9 in
The Ten Biggest Mistakes Of Home Theater Shopping.
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9. Don’t let your spouse or companion persuade you to hide your new speakers inside an antique armoire or entertainment unit. Why buy really good speakers if you're going to place them inside shelving units or armoires? It's the old law of boundary effects. The more surfaces near a speaker, the greater the likelihood of unpleasant sound colorations occurring. A speaker needs to operate more or less in free space. Smaller speakers sound their best on stands. Leave the armoire for electronics and storing CDs!
Regardless, I hope you get the problem solved to your satisfaction.
