As long as the joint is not starved for epoxy and you use the correct drill size for the pilot holes I don't see anything wrong with it. The cam cleat base should spread the load out and keep the screws from acting as pry bars Let's see what the rest of the gang says. 

Laszlo

   Thanks Laszlo...I just caught an error on my part....a 1 x 1, actual 3/4 x 3/4 would be too small on both dimensions for screw depth especially...will likely use more like 1-1/4 x 1-1/4 so the screws dont protrude.

Other builders have thoughts?  Would you put screws on a glue line?

 The Gougeon brothers tested fasteners in shear and found oversizing the hole, then filling with epoxy to bed the fasteners increased the shear strength slightly. This could be used right on a glue line.

The other issue is this: will the shear forces be perpendicular or parellel to the wood grain? If perpendicular, the glue line would stay intact while the wood might split around it.

   Thanks ndadam, good idea about epoxy in the hole...the forces will be sideways to the grain...If I am saying that right. the grain goes athwart, sideways to the boat like the mast thwart...adding bulk to the strengthener rib on the stock dory mast thwart with grain going same way..the screws will hold down cam cleats that will be cleated off by pulling the line aft thru the clam jaws. 

I just realized I have another option...to add a little wood to both the front and back of the mast tnwart strengthener rib and positioning the cam cleat so that the screws go down into the center of the original strengthener rib and the fore and aft pieces I would add help provide a flat surface for the cleat base.   This way, if I could find S/S machine screws long enough I could actually do thru bolts with locknuts underneath...I feel a trip to Lowe's coming on to see if they have the machine screws that long

Curt