14 x 4w is awfully small for a 125...i had a 15 x 4w on my saito 82 in a funtana 40 and it worked fine....despite some people thinking it was overpropped but then i changed to a 14 x 4w and it was better....a 125 should have a much longer prop than a 14inch.

Prop Range: 15x7 - 17x6 according to horizon's website. i would think a 16 x 6 or a 17 x 5....

i have a showtime 4d 90 with a ys110 in it with an apc 16 x 6 and its lots of power....unlimited vertical on cool power 25% heli and pulls out of a hover with authority. i really like the ys because it is light and has much more power than the 125.