Don't have anything there, just the ramp... travelled a few horses that side and never had a problem with them trying to make a bid for freedom! Obviously keep the ramp up and just the top flap open if they are standing on it at a venue.
I have a marlborough conversion that has a thick strap that goes across. Dont travel 2 that often but when i do i make sure the better traveller goes that side
Not overweight with 2 ponies but perhaps 2 horses you would defo be overweight! Also just stick the ramp back up that's allot safer than the belt thing (I know what you mean we have one in ours) x