I have a stall weaver, so while technically not the same, a similar vice in my opinion.
My approach to these types of vices are like you have done at home by not keeping him in a stall - I changed my management style to accomodate how my mare is the least stressed out.
She weaves in the trailer (regardless of if she is loose or in a slant stall of my GN horse trailer) when she gets anxious, but settles during travel.
If I were to need to ship her the distance you are talking about, I would most definitely start her on UlcerGard well in advance of the trip, and continue throughout the trip, and end about a week after arrival in the new location.
I would also trailer her in the box stall - I think with a lot of these vices that horses have (like weaving and stall walking), it’s their mechanism for dealing with stress, and when you take away the ability to handle it the only way they’ve known how, you make them more stressed out.
So I say, give him room to move, and just let him do his thing.