If you use a 48 inch fixture, yes, lay it length wise. Some of the Lowes or Home Depots also sell 2 foot single or dual T-8 fixtures. These are direct wire, not a simple plug in type. This is easliy fixed by buying an extension cord, cutting it and splicing to the fixture. It is really easy to do. The dual fixtures would sit on top of the cage nicely and is balanced by the ligth bulbs. The single fixture would have to lay on its side unless you want to make something to hold it upright.
The 4 foot dual T-8 fixture I got from Lowes is made by Utilitech.
Model # 0313520
It is black in color and runs around $15
I have two "Lithonia Lighting" shop lights that I bought a couple years ago from HD for $20 each. I just added two of the "Utilitech Model # 0313520" lights from Lowes ($13 each) and noticed that they both make an annoying buzzing noise that the others don't. Both brands are electronic ballast models that take 32W T8s. And I ruled out the different bulbs as the culprit by swapping them between the different lights. I thought that buzzing was only a problem with magnetic ballasts, but have since read that inexpensive electronic ballasts can be noisy as well. It's not what I would call "loud", but it's annoying me nonetheless.