battery for GWS tiger moth or pico cub
mAh rating is almost always directly related to weight. The higher the mAh rating, the heavier the battery is. Planes fly better the lighter they are.
The GWS 350mAh pack is the same size as the older GWS 270mAh pack, which does work in the Tiger Moth. It gives you longer flight times and better wind penetration due to the additional weight.