Hi masterjointsmith
I would put two small 3x3 or 4x4 computer fans in the top holes blowing out of the cab.Also two vents at the bottom of the cab one on each side with a third in the back of the cab in the middle top with a 6"fan pulling air out of the cab.I think the computer fans are 25cfm and the 6' fan is 180cfm.I got mind from surpluscenter.com they were under $35.00 for all three.I would put glass under the light about 3" or 4" to seal off alot of heat from the light.
It's a good plan with the cab.Well that's my two cents.
Peace and Happy Token