prey size and weight

[kazz]

Very often I see question about prey size and I think it depends on snake. Pythons can eat up to 5 time bigger prey but corn can't. So this is clear.

And what about weight of prey ? I can see ppl advice to feed small or medium rat. But it don't say about weight.
I feed my python 30% weight from her weight. Why ? I have read scientific article about boas and pythons and they say babies of this snake eat up to 30% from their weight.
Are you bother about food weight ?