So I have a large paint can that I'm looking to convert into a smaller forge and my current debate it whether or not I should build in a pass though/vent hole through the back or if the depth of the paint can and the backflow from the front entry would be enough to get a decent enough fuel air mix. I dont want to be choking my flame necessarily but I also dont want to be wasting fuel heating the neighborhood. Thoughts?

Make a removable back cover? It could be as simple as an IFB or a brick of insulating refractory you cast yourself. I don't use a gas forge, but I know a lot of people block the opening(s) that way.

A small pass through hole in the back is not likely to make problems; if it does, a flap can be mounted over it later.

I wound up cutting a pass through and changing the shape of my refractory liner a bit to allow for a decently strong and flat forge floor. The end thought that sold me was the struggle that heat treat will be without a pass through.