A few years ago I witnessed a masterclass from French guitarist Gabriel Bianco. He started by placing his guitar on his lap, held up his hands and said: "Look no hands!" His guitar was perfectly balanced. Then he said: "All I have to do, is wrap my arms around my guitar. Both arms and hands have now maximum freedom of movement. Any pressure from your arms or hands to hold your guitar, influences your tone. Balance is crucial!"
I tried this at home using my foot stool. No matter how I tried, I couldn't manage to balance my guitar. Then I bought an Ergoplay and found the balance. Conclusion: good posture should result in a balanced guitar without having to correct it with arms or hands. If you can't manage this with the traditional foot stool, try a Dynarette cushion, Ergoplay or other contraption.
Reedition Domingo Esteso by Conde Hermanos 2004; Kenny Hill, model Barcelona 2001
"While you try to master classical guitar, prepare for a slave's life: the guitar will forever be your master and you its slave".