I have always think it's 2x, but how about this?
Chapter: 265 (DBZ 71), P3.4-5
Context: the Great Elder reads Kuririn’s mind and learns of God and Piccolo.
Great Elder: “Hmf! He split in two, long ago…after evil entered into him! How foolish… He diminished by half the genius power with which...
When Gohan "died" fighting against Fat Boo, why were all of them sad about it if he could be revived by the Dragon Balls, even more when he never died and they just asked Shenlong to bring back all people that died in that day?
I think there's a cool way of determining how much stronger Goku got by training with Karin. Just look at Uranai Saga Baba:
Mummy was probably stronger than 21st Budokai Goku, given that Roshi said that Goku probably could not win. Placing Mummy at Goku (vs Blue) level seems accurate.
Goku...
This was the Piccolo who "borrowed" Gohan and Kuririn powers in order to help Goku conclude the Genki-Dama. Going by the Daiz numbers, Piccolo would probably end up stronger than Vegeta lol.