Yes, the Vanagon is pretty air tight making the doors hard to close. But you
don't have to slam them if you use firm pressure during the last few inches.
For closing the slider, I learned this trick years ago from, believe it or
not, a VW salesman. Since in the later models the latch is at the rear of
the door, as you slide the door closed, put your left hand at the rear of
the door and push in. Makes it much easier to close.