Mike, got all of that ! Frank
and the last one for tonight..... a screenshot of a program I wrote in 2009...... it allows you to change the variables and gives the maximum angular difference between the left and right banks of 48IDA's. I used it for a competition for a local college open day where students were invited to 'optimise' the numbers and the lowest angular difference got an ipod. In return I got an optimised geometry....... ;-) trouble is I lost the optimum numbers and am now running the program again...only 11 years later...... wow...... what happened? ...... I got old.........