In an IDF at one of our facilities, we have a busbar grounded to the ufer, and all racks, cable runway, and a couple BETs grounded to the busbar. The busbar is a smaller CPI model, however this particular one that we installed previously in the room, prior to a recent expansion, didn't have enough pre-punched holes to accommodate additional equipment. We had another identical unit in stock, so that was installed next to the original. The question, though, is whether it's legal or code-compliant to bond one to the other, and if so, what's the best method, and what conductor size should be used? The conductor from the ufer is #0 or #1, and all other conductors are #6. The other option, if necessary, is to replace both smaller busbars and buy a single, larger busbar with enough space to accommodate all connections. Thanks in advance for the advice.