Step 1: Specify the size of each individual glass unit.
Width: 1/16 1/8 3/16 1/4 5/16 3/8 7/16 1/2 9/16 5/8 11/16 3/4 13/16 7/8 15/16 inches W Length: 1/16 1/8 3/16 1/4 5/16 3/8 7/16 1/2 9/16 5/8 11/16 3/4 13/16 7/8 15/16 inches L
IBP carries 23 1/8" modular units as an in-stock item with a slip-resistant circle dot frit on the top surface, in your choice of clear or obscure glass. This size allows you to place a two-wide grid in a containment opening exactly 4 feet wide, as illustrated in this PDF file.
Step 2: Now build an installation using the units you just sized!
P.S. Remember, IBP offers free design assistance for all GlassWalk floor systems. If you prefer, submit your custom layout, and we will work up preliminary drawings for your review.