Attempting to use a upward variance without extra powder

[Leoterelli250]

Let's say I would like to make 400ml of sust and have 100g raw powder, and I want to make sure each ml is either exactly 250mg/ml or over. So would it be possible to shorten my total volume to 390ml, thus needing only 97.5g, but still using the 100g? Would this ensure every ml is either 250mg/ml or over as long as I add my bb/ba to the total amount according to 390ml as well? Also, for those who have brewed sust while you are here can someone give me advice on the ba/bb ratio for sust? I have seen when in doubt do 2/20, but many recipes for sust I have also seen ratios at 2/7.5 and etc. I just do not want my stuff to crash. Thank you.

[Newyear1]

To make sure , use a little less oil, and keep ba, and bb the same and you should be fine