The answer is, comparing the craters on the moon with diameter of the moon.
Firstly, lets look at craters on the moon.
Most of the theories depend on these craters are fallen meteors; ie in fact, according to flat earth theory, they are fallen stars.
So, all we need compare their apparent size to moon's apparent size. By arriving a ration, we can calculate their diameter by using ratio and comparing moon's actual size.
lets do it.
I have marked 4 craters. One of them is the biggest one; another one is a big one, another one is an average one, and two small others.
I have measured the biggest one as 1/10 of the diameter of the moon.
According to viki the diameter of the moon is 32 miles, ie 50kms. I want to use this value, although I think it may be smaller as 25 kms. Anyways.
Diameter of The biggest star: 1/10 x50kms= 5kms.
The biggest star is 5 kms diameter. Average stars are 1~2 kms.
Smallest one about 1000 times smaller than moon.
The smallest stars about: 50kms x 1/1000 = 50 metres.
So;
The diameter of the stars are between 50 metres ~ 5 kilometres.