Installing pendant lights - no junction box available/feasible
When I remodeled, and moved my kitchen from one side of the house to the other, I installed an electrical outlet above the stove for a microwave. The inspector said that was fine, however I had to use an extender to get the box into the cabinet. He didn't want to see a cut out in the cabinet and the cord going through to the outlet. So I installed an extender to get the box into the cabinet. He said it was perfect and signed me off. So I say install an old work box in the upper older soffit and install an extender on that to get it out to the plywood. Another option, if you have a junction box now, you could install external pendant lights that swag and hook to the underside. Just would need to wire both into the central box you have now and swag the cords to where you want.