Blocksizes when plotting

Im thinking about optimizing my disk space upon the following calculator:

I have some questions:

  • Do you have experience with that calculator? How precise is it? I have noticed blocks may vary in size some ~2 percent. Additionally I have seen Harddrives vary to some degree. Im a little afraid plotting a k33 or k34 block and shooting over the space limit.

  • have you found it worthwhile to plot larger plots?

  • whats your approach writing k33 or k34 blocks (temp size)? (aside from large disk arrays just for plotting, my farm is still quite small)