I've just been playing with iron tanks in SSP, bit of titbits for you which you may know/not know.
- when building a tank only the edges need to be iron tank walls, the rest (inc top and bottom) can be tank glass.
- tank sizes are 3x3 5x5 7x7 but can be 8 high
- the storage information (if your tank contains liquid) is stored in the bottom centre block
- going on the storage information if you wanted to expand say a 3x3 to a 5x5 do so by building 1 out all the way around so the centre bottom block is still the centre bottom block, this will retain any liquid that was inside
- you can place tanks on top of each other by putting a connecting valve in the middle of each tank so they are facing, when you do this a valve acts for both tanks
- valve's can be placed anywhere except edge blocks but only pump liquid in or out on rows 2 & 3 from the bottom
- if your tank contains liquid you can break a block (so long as it's not the storage block) and when made a tank again the liquid is retained
- you can place Railcraft liquid loaders and unloaders next to valve's without the need for pipes and they will load/unload the liquid.
- when looking at the volume of the tank, 1 bucket is 1,000 of the tank liquid
- a max size tank holds 6,272,000 liquid or 6272 buckets worth of liquid