Needed these lights for a project and adapted from from Graham's KitcheAdobe (I think) but could have been Renerabbit.
Vertical 42" and horizontal 54". Adjust as you please. (and if you make a few sizes might post them back here eh?
A few depths of shelves (job had changes) that you insert into the back of the cabinet so that to hide the lights and let them shine.
Image only has the horizontals. Since they decided on books the verticals were not used.