"Robert Rushing" wrote in message
...
I would like some input on a built in desk I'm building. The overall
length
will be 8'6" and 23" deep. The desk will be built from MDF. (Yes I know
many would suggest using a quality plywood, but the MDF was free 5 sheets
of
3/4 4x9.) The desk will be supported by basically two boxes 34" wide on
each end leaving roughly 36" in the middle for an work area. The desk top
will be supported all the way across the front and back edge.

It should be OK with the support you have.

Only problem I see is the weight. Unless your wife has a fork lift truck,
it will never get moved for cleaning.