If using 1.1 you can scale the animation directly. If using 1.0 or lower you can set
scale = 0.5,0.5 on the explod creation. If for some obscene reason it's a helper you can do
[state angledraw]
type = angledraw
trigger1 = 1
scale = 0.5,0.5
Although all transparency must be in code form at that point too and will not work through animation settings.