I have the www.microheli.com blade cp tail upgrade on my blade, it's good for a 5mm shaft. The motors last alot longer this way, well over 4 times what the stock motor would last on the blade series, although I dunno much about the axe. The main reason they last so much longer is because they run so much cooler. Mine is basically +10F over ambient, compare to the 80 to 100F over ambient of the stock tail.

The dual tail setups run an n30 motor, compared to the bigger n60 on the axe. You might have to buy a blade series gear and tail prop of the one from the axe wont fit. I also don't know how the thrust would differ. The dual tail runs 1.26A on a 3s lipo, the n60 is likely to be 2 to 2.5A, so you'll get slightly longer flight times.

GL, and welcome to RCU [8D]