Will it be way too small? I have a cob at the moment that doesn't seem to have any effect at all as it looks a bit big? But woulsn't a pony one be far too small?
i think it depends what brand it is. i have a cob size on my 16.2 and the straps with the metal rings that attach to the reins are only just short enough to have an effect. it is really old though so probs different to the cob sizes around now!
trial and error's probably the best way to find out