What height are they?

@Background Pony #7911
 
That would make no sense whatsoever.

@Background Pony #5563
 
First of all, fashion designers on Earth don’t have to be the same as fashion designers on Equestria, you moron, so that argument is null and void, because you’re comparing horses to humans.
 
Second of all, the main reason to Hootershy’s popularity is the anime logic of “It’s always the quiet ones”. The shy girls have the biggest of racks and are virtually the hottest. It also coincides with the fact that she hates too much attention and yet has things that make people more attentive to her presence. Then there’s the fact that someone as kind and gentle as her has such a great bod means that he who gets the honour of being her husband gets a helluva reward.
 
Thirdly, she’s probably the least active of the Mane Six or at least the least athletic and energetic, so a good portion of fat will be stored up in her body.
 
Also, there are MANY fashion models with big tits, so that renders your argument even more moot.
 
Tl;dr: You’re a moron. Don’t talk about this as you have no basis at all.

@Viron13  
They’re not short, they’re among the avergage female’s height

I don’t get why people think fluttershy would have a large chest. For one she was a fassion model. Go look up some images of fassion models. Go on I’ll wait… Fucking small tits. None of them have large breasts and most have abjectly small ones. This is because fassion designers hate haveing to work their dresses around the models breasts.
 
Then people go on and say “lolol shy girls got huge tits! Obviously.” Personally I have never met a shy girl with any thing larger than c. If they had large breast I think they would most likely be less shy.

They are all so very, very short.

I’d switch Fluttershy with Rarity.

Huh. I haven’t seen much of any flat Pinkie Pie.  
Dash switched with her or maybe even AJ switched with Rarity (outdoor work = less body fat)

Some people views a humanized Pinkie Pie as flat chested, some other big breasted. Generally, though, there’s much more agreement on the other charachters (AJ, Fluttershy = big, RD = small, TS = medium-small, Rarity = medium-big).