Gilbear
Here's what you are looking for!!
The Vol. 4 Issue 21 of
Shopnotes has a 4 page an article titled
" Router Thicknessing Jig " which uses the router to plane boards on a adjustable platform bed similar to that mentioned by Doug with a few modifications.
Modifications include a clamping system, adjustable width up to 15-3/4" wide, and carriage support for the router.
They use a 1" dia. 1/2 ' shank bottom cleaning bit to achieve the cut.
If you don't have that issue, I'll see if I can somehow copy this article and email it to you.
(You didn't hear that, right??) 
Ric