Question on full sheet acrylic top brace

[PapHater]

I've got a quick question placing a full sheet of acrylic for the top base; is it better to place the piece in between the walls or rest it on top similar to how the bottom piece is welded? My tank won't be very tall so I'd really like to avoid having the bracing take up an extra space. The tanks dimensions will be 94x22x22 (only be filled to around 20" high).

 

[poppalina]

Place on top of the outside walls, just like the bottom.