Very impressive. You mentioned the tongue weight. Is there any reason the trailer is designed to have so much weight so far forward of the axle? Seems a centered axle would be more suitable. I know you wouldn't want the load lifting the bike.
Ive wondered the same thing but I have always just tried not to second guess the folks at "bikesatwork.com".
Putting the wheels in the rear of the trailer will put a lot of weight on the rear wheel of the bike. That means the rear wheel is unlikely to skid/slip under acceleration or braking. Assuming the trailer tongue+hitch and the bike's rear wheel/frame are strong enough, the rear wheel is the best place to put a lot of weight. (because it's used for power and for braking.)