Hey there wellsweb62, thanks for your message and I’ll be gentle I promise 🤞
Too little “pressure” will result in a weak, unsupported sound.
Too much and the feeling of freedom required i.e. humming/singing will be compromised and the BCH (Body’s Concert Hall) will close it’s doors and you will experience back pressure and strain in the throat and chest.
There are French Horn leadpipe packs you can get where you can work on your “sympathetic oscillation”.