When you have some economists saying that leaving the EU will be disastrous for the UK's economy, and other economists saying that it could be beneficial for the UK economy, how are you supposed to know who to believe?
There is a key difference between Patrick Minford's hypothesis and the economic papers often quoted by remainers. Patrick Minford's hypothesis is not a peer-reviewed published paper, it is nothing more than a press release.
However, the predictions are still dire. Yes, it predicts a 4% increase in trade after Brexit, but it also predicts the almost complete elimination of the manufacturing sector from the UK, and predicts that the poor will get poorer whilst the rich get much richer.
This hypothesis relies on the UK unilaterally abolishing all trade tariffs and product safety standards!
His press release wouldn't manage to get past the peer review stage of publishing an academic paper for several reasons.
It completely ignores a fundamental economic model known as the Gravity Model. This is fine as long as you invent a Star Trek style teleportation machine that is completely free to use (you can't ignore geography and product transportation costs!)
On top of this, the hypothesis has been widely criticised by other economists because he's managed to get his maths wrong.
In summary, there is not a single peer-reviewed economic paper forecasting a positive outcome for Brexit.
There are VERY few economists who support brexit, but the newspapers have managed find them and push their unfounded and illogical arguments, even though they are vastly outnumbered by almost all academic economists worldwide who view Brexit as a disaster.