Just for information purposes, that 300 lb. scale would be worthless (crushed) after I place the hitch of my gooseneck on it. I'm also not saying that your scale method is not worthy of intermittent use for a bumper pull trailer. But, with experience, eventually the person doing the hauling will develop the knowledge and feel for where that load needs to be placed to ensure an acceptable tongue weight.
May I ask, just how much experience you have with gooseneck trailers? Regardless of what bumper pull trailer you use, the tongue weight empty does not begin to compare with that of a gooseneck.
New to this forum. I see it can get a bit "snippy". Or am I being a bit sensitive?
As a matter of fact, I rarely use a tire air pressure gauge. When I have, I'm normally within a couple of pounds or the desired AP. But, I also know what my tires should look like when the trailer is empty and when it's at max load.