I've never done this with t-molding, but I've done it with other molding, and I don't think it will show unless you point it out to someone. My own cab is full of tiny flaws that are clear as day if I point them out, but are impossible to detect normally.
However...

Since routing a groove is difficult to undo if you change your mind, do a test piece first. Take a piece of scrap wood and cut the t-molding groove. Then put a small strip of your t-molding in there and cope another small piece.
See how good a fit you can get.
You can get a sample pack from t-molding.com if you don't want to invest in buying all you molding before you've made up your mind.
Also, the only place I would consider doing this would be here:

All the other joints I would use continuous t-molding. If you don't like how it wraps around these other corners, you might consider softening them by rounding them over (just a bit). I don't mean putting a one inch radius on all your corners, just enough to get the t-molding to bend better. Again, you can use a piece of scrap wood to see what minimum radius works for your cab