Good idea to mix at a high concentration if it can be done. Probably not a good idea to keep A and B separate. Wouldn't there be a preservative in one and not the other?(posted 8212 days ago)I think I read in a Google rec.photo.darkroom that someone had successfully mixed Xtol stock at double strength (i.e. half the volume of water). I avoided xtol because of the reports of failure, but there are good reports of it for my favourite film, Neopan 400.
I have a 5 Litre pack unused, so i'll try to dissolve it in less water, and see what happens. If Part A dissolves, and then Part B doesn't, then more water would need to be added. I'll let you know.