I had the same need to carry 4 bikes. For years I tried to be cheap and carried two on the strap bike rack on the back hatch and two inside the van between the two front seats. The two inside the van had to be disassembled. It was once a year for our annual Yosemite camping trips. 

Do yourself a favor and get yourself a tow hitch like this one. 
http://www.gowesty.com/ec_view_details.php?id=2582&category_id=&category_parent_id=
The installation is super easy and I am asking why didn't I get one sooner.

For the four bike hitch rack, go on your local CL and spend $100-200 to buy it off of the guy who upgraded his or moved onto the next gadgety hobby. 

James

Sent from my iPhone

> On May 5, 2014, at 7:51 AM, Maureen Hall <maureenehall@YAHOO.CA> wrote:
> 
> Hi folks
> 
> I want to transport up to 4 bikes on my '91 Westy. Should I go with a rack that holds four on the back? Should I put a couple of bikes on the front and a couple on the back to balance the load? What's best practice for bike racks?
> 
> Maureen
> '91 Westfalia