I have a B-E-A-D-G set of TI flats tuned up a 4th to E-A-D-G-C. The tension is very high, but very fast and still thuddy. The TI strings in normal tuning were too floppy for my taste, and I hated every high C string I tried. So on a lark, I put a TI G string on as a C and tuned it up. I liked the feel and sound, so eventually I ended up changing out all the strings that way. You could experiment with this concept by tuning up of your stock tapes up a whole step or so and seeing if you like the response. For me, it was a real pandora's box!
It makes a lot of sense and should be to bad tension wise since it's like having a capo on a standard 5 string b-g at the 5th fret
