The width is 3 5/8 inside to inside and the height is 2 3/4 inside to inside.
The 1.5 bottle widths are 4 1/8 inside to inside and height is 3 3/4 inside to inside.
Hope this helps. I got the plans off e-bay they included plans to build the following: large hydralic press, 5gal hydralic press, glue applicator, carboy protectors, carboy dolley, bottle carrier, fermenter cradle, insturment holder, siphoning table, carboy lifter, punch down tool.
It was a CD with the pdf files for only 9.00
Good luck with your rack