Dear Kangjoo,

The experiment that originally motivated me was to plot the standard deviation of correlation coefficients across bootstrap samples, as a function of block length. The rationale was to have as pessimistic a view as possible, and to maximize variability. The results of this experiment are presented in (Bellec et al, 2008) http://www3.stat.sinica.edu.tw/sstest/ol... Figure 3.1 (see text beginning of section 4.3 for the results, and end of section 2.2. for the procedure). The experiment is actually about differences in correlation coefficients, but I got similar results on the coefficients themselves (not shown). The dependency between h (block length) and the std of correlation values is smooth with a clear maximum. Parameter h does not seem to have a big impact within a reasonable range. So for BASC I decided to randomize it. The sqrt(T) centered interval is more or less arbitrary but was inspired by the curves from the paper. 

I guess you could easily reproduce the experiment for multiband data, and see if the same kind of behaviour is observed. 

I hope this helps, 

Pierre