> I've seen folks with something on their back window, looks like
a plastic
> rectangle that sticks on from the inside so they can see
better.  Does this
> really work?  I don't know what it is called.

the best ones are by 3M and are called Vangard. they are
available at RV suppliers (but they usually have only the largest
size) and sometimes at local auto parts dealers that sell 3M
paint/bondo/etc for use on your cars.

yes, it really works. best thing is the angle ... it shows you
what is right down beside your bumper, so you don't back over
something, and what is right beside at the rear.

> Is there a preferred size?  Also some put in dead center,
others more towards
> passeger side. ..which is better placement?

i like the smaller size. it's 6x8 inches and doesn't obscure too
much of my regular rearward vision throught the rear window.  i
also like the dead center arrangement, just because it allows me
the same field of vision on both sides of the bus. but you can
sit in the driver's seat and have someone hold the Vangard up on
the rear window and see how it looks to you.

> Where do you buy?  Do they really stay on or can they get moldy
as some that
> I've seen are brownish around the edges.

check these for more info and prices ...
http://go-rv.com/online/1126/showproductdetails?catid=1893

http://www.go-rv.com/online/1060/showproductdetails?catid=1893

and other local places that sell such stuff .

yes, they really really stay on ... just follow the directions
carefully and you'll be ok. the big trick is to clean, clean,
clean the rear window surface before you put it on. then squeegee
all the water out from under the lense .. i use those yellow soft
plastic bondo-spreaders that you can buy at wal-mart for like
$3/pack.  i think the brownish around the edges is just due to
aging of the 'glue' that's used. according to the directions, you
can always remove it and reapply it on another vehicle ...

good luck!
joel