You might want to do a search on this topic, although I don't know what you'd use as a search, maybe "middle pickup" but for me, the reduced output is preferred. It's what cleans up the amp, and produces the widest tonal variation in the in between configurations. Apparently Vai feels that way too, since the Jem single is more vintage than hot in output. I myself like a real glassy, clean single in the middle.
The fast track 1 is a good higher output yet still glassy-clean middle pickup if you need it, but it will throw the look of the Jem off. I think it would look good, but not stock. Any true singles that boast higher output would also have some degree of high frequency loss or at least an overshadowing of the high freqs by the mids, and that tends to wash out the snappy attack of the in between positions.