wow, well done, they are adorable. I can't remember the size of mine but I will check when I get home. My mares were a lot smaller though so not sure mine will help.
It is great that you are prepared, I am not a lover of putting blankets on babies but sometimes you have no choice.
This little guy had to wear two plus a hot water bottle when he was sleeping, the weather had turned so cold and he was having trouble regulate, it only took a week or so for him to get stronger though luckily.