The plane does not need weight in the tail, that just depends on your motorization! If you fly with a YS63 or heavier 4-stroke you will need lead to get a good CG position, If you use a .50 2-stroke the CG is just fine. I fly my Oxalys 50 with an OS50SX and Hatori Copy tuned pipe (pictures on page 11 of this thread), no lead whatsoever, lightest take-off weight possible and still unlimited vertical performance...