As far as rez size goes....it's completely up to you and how much work you are willing to do to keep things in balance. Smaller rez, more monitoring of numbers and more rez changes, more nutes etc etc...(ps...I love it when rhizome says things like "biomass ratio") As long as you keep your share of it in order the plants don't really care.
As Rhizome said....the ratios are important to keep in balance. It doesn't take long at all for numbers....while looking similar to you.....look very different to your plants and we all know it's not about you.....it's about the plants.