The diameter will be the limiting factor... smaller the diameter, will leave a shorter depth for an upper shelf.
The Lang 48 - is 24 x 48, only had a partial wdith/partial depth upper shelf.
The Klose BYC - is 20 x 48, and also has a partial upper shelf.
[The Klose is just large enough to place hotel pan raised screens front to back... useful for wings - 15/tray]
Below is the actual dimensional breakdown (when I had to add a full width second shelf in the 60) showing the available cooking surfaces between the Lang 48 and 60. Note the upper shelf specs.
Lang 48 (listed capacity @ 10 butts)
Upper rack 13.5 x 33.5 452.25 sq. in. 3.14 sq. ft.
Lower rack 22.5 x 42.5 956.25 sq. in. 6.64 sq. ft.
total 9.78 sq. ft.
Lang 60 (listed capacity @ 20 butts)
Upper rack 13.5 x 35.5 479.25 sq. in. 3.33 sq. ft.
Upper rack 22 x 44 (new) 968 sq. in. 6.72 sq. ft.
(44.71%)
(double the size of original grate - bigger than the Lang 48 main grate)
Lower rack 23 x 52 1196 sq. in. 8.31 sq. ft.
(55.29%)
Lang 48 patio 9.78 sq. ft.
Lang 60 specs - 11.62 sq. ft -[18.9 % larger than the 48]
With new shelf - 15.03 sq. ft. [30% larger than stock 60]
[54% larger than the 48]
