I've done it and it works. Poor man's posi but you can do it 1 of 3 ways. You can add extra side gear shim to each side for a solid traction lock but will wear out in less than 6 months, you can add an extra shim to each spider gear which will give the same effect and last the same amount of time, OR you can add an extra shim to each spider gear and each side gear for a super tight posi that will last longer(as long as you don't do a long 1 wheel burn out and be careful to make sure both tires are spinning while doing burn out). That latter one will act almost like a spool but will slip around corners if using very sticky tires otherwise with regular street tires it will stay locked around a turn like a spool. I have done it to several 8" and a couple 9" pumpkins and I can honestly say if you don't have the money for a traction lock, this will get you thru.
I just read that artical and it is true but he failed to mention using the same technique on the spiders since you have to remove the pins where they ride anyway and that shims the spiders inward more creating the same pressure wedging harder against the side gears so that doubles the effectiveness with the shimming of the side gears as opposed to just shimming the side gears with extra washer. It lasts much longer too.
I did this in my 8 inch until I got the locker.Its just like 89coupe says works good but doesn't last to long.Actually it worked ok for me on street radials until I started running the McCreary's and then it wore out very quickly.I think the sticky tires forced it too turn the one wheel around corners where as before there was some slippage on the radials.I only shimmed the two side gears,so doing all 4 would probably last longer.