Hi Eliana and thanks for your questions! Here is the info:
Shelf is not tested to hold a certain weight capacity, but I'd suggest 50-60 lbs or less. The more weight added will cause shelves to sag.
The manufacturer will not modify the unit. It is possible to do this if you purchase.
See MRT-HO3684B for 84" bookcase.
Answered on 12/5/2016 by Anonymous