Not sure about your design. The BGR idea for the 5 groups of 60 makes sense. In what way do you need the items broken into 2 groups within the larger groups? You had two sets of 30 within each group of 60--both randomized, right? If so, did you always have 30 WGRs of 1 and 30 WGRs of 2? If so, the problem may be that you need to use 3's and 4's for the second group of 60, 5's and 6's for the one after that and so on. Otherwise all the items with a WGR of 1 across all of your big groups will be randomized with each other and I don't think you don't want that!