You're using the correct ratio, which is 11:3, Alex Martinez.
As of now, the option to add the signature on the line isn't available. QuickBooks design it this way, so it fits into a 2-3/4 inch wide by 3/4 inch tall space signature.
I'll take note of your idea and share it with our developers. They'll evaluate your suggestion and may be added to our product updates.
When you're ready to print checks, you can take a look at this article: Print Your Paychecks In QuickBooks Desktop.
Also, your attached photo has been removed to protect your data.
I'm just a post-away if you need help. Keep safe!