tounge and grove question

I’d put the groove in the plywood so as to not have problems chipping the veneer.

-- Joe

I usually put the tongue on the banding by putting the tongue on first and then cutting to width.

-- W James Brokenbourgh Custom furniture maker http://artisticwoodstudio.com/

I would just put a work support to either side of the router table and cut the groove in the plywood there. 78” isn’t small but with simple supports to help out you shojldn’t have any problems on the router table.

-- Tom Hintz, www.newwoodworker.com

I go with Jim. Put the tongue on the 1 X 4. You can use a guide clamped on the plywood to guide the router as you cut the grove in the edge. I would use a slot cutting router bit with a bearing and have the bearing ride on the clamped on guide.
Another alternative is to use biscuits for alignment and support.

-- Les B, Oregon